Chapter 8. Client and Utility Programs

Chapter 8. Client and Utility Programs
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8.1. Overview of the Client-Side Scripts and Utilities

The following list briefly describes the MySQL client programs and utilities:

myisampack
A utility that compresses MyISAM tables to produce smaller read-only tables. See Section 8.2, “myisampack — Generate Compressed, Read-Only MyISAM Tables”.
mysql
The command-line tool for interactively entering SQL statements or executing them from a file in batch mode. See Section 8.3, “mysql — The MySQL Command-Line Tool”.
mysqlaccess
A script that checks the access privileges for a hostname, username, and database combination.
mysqladmin
A client that performs administrative operations, such as creating or dropping databases, reloading the grant tables, flushing tables to disk, and reopening log files. mysqladmin can also be used to retrieve version, process, and status information from the server. See Section 8.5, “mysqladmin — Client for Administering a MySQL Server”.
mysqlbinlog
A utility for reading statements from a binary log. The log of executed statements contained in the binary log files can be used to help recover from a crash. See Section 8.6, “mysqlbinlog — Utility for Processing Binary Log Files”.
mysqlcheck
A table-maintenance client that checks, repairs, analyzes, and optimizes tables. See Section 8.7, “mysqlcheck — A Table Maintenance and Repair Program”.
mysqldump
A client that dumps a MySQL database into a file as SQL statements or as tab-separated text files. Enhanced freeware originally by Igor Romanenko. See Section 8.8, “mysqldump — A Database Backup Program”.
mysqlhotcopy
A utility that quickly makes backups of MyISAM or ISAM tables while the server is running. See Section 8.9, “mysqlhotcopy — A Database Backup Program”.
mysqlimport
A client that imports text files into their respective tables using LOAD DATA INFILE. See Section 8.10, “mysqlimport — A Data Import Program”.
mysqlshow
A client that displays information about databases, tables, columns, and indexes. See Section 8.11, “mysqlshow — Display Database, Table, and Column Information”.
perror
A utility that displays the meaning of system or MySQL error codes. See Section 8.14, “perror — Explain Error Codes”.
replace
A utility program that changes strings in place in files or on the standard input. See Section 8.15, “replace — A String-Replacement Utility”.

MySQL AB also provide a number of GUI tools for administering and otherwise working with MySQL servers. For basic information about these, see Chapter 4, Using MySQL Programs.

Each MySQL program takes many different options. However, every MySQL program provides a --help option that you can use to get a full description of the program's different options. For example, try mysql --help.

MySQL clients that communicate with the server using the mysqlclient library use the following environment variables:

`MYSQL_UNIX_PORT`	The default Unix socket file; used for connections to `localhost`
`MYSQL_TCP_PORT`	The default port number; used for TCP/IP connections
`MYSQL_PWD`	The default password
`MYSQL_DEBUG`	Debug trace options when debugging
`TMPDIR`	The directory where temporary tables and files are created

Use of MYSQL_PWD is insecure. See Section 5.8.6, “Keeping Your Password Secure”.

You can override the default option values or values specified in environment variables for all standard programs by specifying options in an option file or on the command line. Section 4.3, “Specifying Program Options”.

8.2. myisampack — Generate Compressed, Read-Only `MyISAM` Tables

The myisampack utility compresses MyISAM tables. myisampack works by compressing each column in the table separately. Usually, myisampack packs the data file 40%-70%.

When the table is used later, the information needed to decompress columns is read into memory. This results in much better performance when accessing individual records, because you only have to uncompress exactly one record.

MySQL uses mmap() when possible to perform memory mapping on compressed tables. If mmap() does not work, MySQL falls back to normal read/write file operations.

Please note the following:

If the mysqld server was invoked with the --skip-external-locking option, it is not a good idea to invoke myisampack if the table might be updated by the server during the packing process.
After packing a table, it becomes read-only. This is generally intended (such as when accessing packed tables on a CD). Allowing writes to a packed table is on our TODO list, but with low priority.
myisampack can pack BLOB or TEXT columns. The older pack_isam program for ISAM tables cannot.

Invoke myisampack like this:

shell> myisampack [options] filename ...

Each filename should be the name of an index (.MYI) file. If you are not in the database directory, you should specify the pathname to the file. It is permissible to omit the .MYI extension.

myisampack supports the following options:

--help, -?
Display a help message and exit.
--backup, -b
Make a backup of the table data file using the name tbl_name.OLD.
--debug[=debug_options], -# [debug_options]
Write a debugging log. The debug_options string often is 'd:t:o,file_name'.
--force, -f
Produce a packed table even if it becomes larger than the original or if the intermediate file from an earlier invocation of myisampack exists. (myisampack creates an intermediate file named tbl_name.TMD in the database directory while it compresses the table. If you kill myisampack, the .TMD file might not be deleted.) Normally, myisampack exits with an error if it finds that tbl_name.TMD exists. With --force, myisampack packs the table anyway.
--join=big_tbl_name, -j big_tbl_name
Join all tables named on the command line into a single table big_tbl_name. All tables that are to be combined must have identical structure (same column names and types, same indexes, and so forth).
--packlength=len, -p len
Specify the record length storage size, in bytes. The value should be 1, 2, or 3. myisampack stores all rows with length pointers of 1, 2, or 3 bytes. In most normal cases, myisampack can determine the right length value before it begins packing the file, but it may notice during the packing process that it could have used a shorter length. In this case, myisampack prints a note that the next time you pack the same file, you could use a shorter record length.
--silent, -s
Silent mode. Write output only when errors occur.
--test, -t
Do not actually pack the table, just test packing it.
--tmpdir=path, -T path
Use the named directory as the location where myisamchk creates temporary files.
--verbose, -v
Verbose mode. Write information about the progress of the packing operation and its result.
--version, -V
Display version information and exit.
--wait, -w
Wait and retry if the table is in use. If the mysqld server was invoked with the --skip-external-locking option, it is not a good idea to invoke myisampack if the table might be updated by the server during the packing process.

The following sequence of commands illustrates a typical table compression session:

shell> ls -l station.*
-rw-rw-r--   1 monty    my         994128 Apr 17 19:00 station.MYD
-rw-rw-r--   1 monty    my          53248 Apr 17 19:00 station.MYI
-rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm

shell> myisamchk -dvv station

MyISAM file:     station
Isam-version:  2
Creation time: 1996-03-13 10:08:58
Recover time:  1997-02-02  3:06:43
Data records:              1192  Deleted blocks:              0
Datafile parts:            1192  Deleted data:                0
Datafile pointer (bytes):     2  Keyfile pointer (bytes):     2
Max datafile length:   54657023  Max keyfile length:   33554431
Recordlength:               834
Record format: Fixed length

table description:
Key Start Len Index   Type                 Root  Blocksize    Rec/key
1   2     4   unique  unsigned long        1024       1024          1
2   32    30  multip. text                10240       1024          1

Field Start Length Type
1     1     1
2     2     4
3     6     4
4     10    1
5     11    20
6     31    1
7     32    30
8     62    35
9     97    35
10    132   35
11    167   4
12    171   16
13    187   35
14    222   4
15    226   16
16    242   20
17    262   20
18    282   20
19    302   30
20    332   4
21    336   4
22    340   1
23    341   8
24    349   8
25    357   8
26    365   2
27    367   2
28    369   4
29    373   4
30    377   1
31    378   2
32    380   8
33    388   4
34    392   4
35    396   4
36    400   4
37    404   1
38    405   4
39    409   4
40    413   4
41    417   4
42    421   4
43    425   4
44    429   20
45    449   30
46    479   1
47    480   1
48    481   79
49    560   79
50    639   79
51    718   79
52    797   8
53    805   1
54    806   1
55    807   20
56    827   4
57    831   4

shell> myisampack station.MYI
Compressing station.MYI: (1192 records)
- Calculating statistics

normal:     20  empty-space:   16  empty-zero:     12  empty-fill:  11
pre-space:   0  end-space:     12  table-lookups:   5  zero:         7
Original trees:  57  After join: 17
- Compressing file
87.14%
Remember to run myisamchk -rq on compressed tables

shell> ls -l station.*
-rw-rw-r--   1 monty    my         127874 Apr 17 19:00 station.MYD
-rw-rw-r--   1 monty    my          55296 Apr 17 19:04 station.MYI
-rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm

shell> myisamchk -dvv station

MyISAM file:     station
Isam-version:  2
Creation time: 1996-03-13 10:08:58
Recover time:  1997-04-17 19:04:26
Data records:               1192  Deleted blocks:              0
Datafile parts:             1192  Deleted data:                0
Datafile pointer (bytes):      3  Keyfile pointer (bytes):     1
Max datafile length:    16777215  Max keyfile length:     131071
Recordlength:                834
Record format: Compressed

table description:
Key Start Len Index   Type                 Root  Blocksize    Rec/key
1   2     4   unique  unsigned long       10240       1024          1
2   32    30  multip. text                54272       1024          1

Field Start Length Type                         Huff tree  Bits
1     1     1      constant                             1     0
2     2     4      zerofill(1)                          2     9
3     6     4      no zeros, zerofill(1)                2     9
4     10    1                                           3     9
5     11    20     table-lookup                         4     0
6     31    1                                           3     9
7     32    30     no endspace, not_always              5     9
8     62    35     no endspace, not_always, no empty    6     9
9     97    35     no empty                             7     9
10    132   35     no endspace, not_always, no empty    6     9
11    167   4      zerofill(1)                          2     9
12    171   16     no endspace, not_always, no empty    5     9
13    187   35     no endspace, not_always, no empty    6     9
14    222   4      zerofill(1)                          2     9
15    226   16     no endspace, not_always, no empty    5     9
16    242   20     no endspace, not_always              8     9
17    262   20     no endspace, no empty                8     9
18    282   20     no endspace, no empty                5     9
19    302   30     no endspace, no empty                6     9
20    332   4      always zero                          2     9
21    336   4      always zero                          2     9
22    340   1                                           3     9
23    341   8      table-lookup                         9     0
24    349   8      table-lookup                        10     0
25    357   8      always zero                          2     9
26    365   2                                           2     9
27    367   2      no zeros, zerofill(1)                2     9
28    369   4      no zeros, zerofill(1)                2     9
29    373   4      table-lookup                        11     0
30    377   1                                           3     9
31    378   2      no zeros, zerofill(1)                2     9
32    380   8      no zeros                             2     9
33    388   4      always zero                          2     9
34    392   4      table-lookup                        12     0
35    396   4      no zeros, zerofill(1)               13     9
36    400   4      no zeros, zerofill(1)                2     9
37    404   1                                           2     9
38    405   4      no zeros                             2     9
39    409   4      always zero                          2     9
40    413   4      no zeros                             2     9
41    417   4      always zero                          2     9
42    421   4      no zeros                             2     9
43    425   4      always zero                          2     9
44    429   20     no empty                             3     9
45    449   30     no empty                             3     9
46    479   1                                          14     4
47    480   1                                          14     4
48    481   79     no endspace, no empty               15     9
49    560   79     no empty                             2     9
50    639   79     no empty                             2     9
51    718   79     no endspace                         16     9
52    797   8      no empty                             2     9
53    805   1                                          17     1
54    806   1                                           3     9
55    807   20     no empty                             3     9
56    827   4      no zeros, zerofill(2)                2     9
57    831   4      no zeros, zerofill(1)                2     9

myisampack displays the following kinds of information:

normal
The number of columns for which no extra packing is used.
empty-space
The number of columns containing values that are only spaces; these occupy one bit.
empty-zero
The number of columns containing values that are only binary zeros; these occupy one bit.
empty-fill
The number of integer columns that do not occupy the full byte range of their type; these are changed to a smaller type. For example, a BIGINT column (eight bytes) can be stored as a TINYINT column (one byte) if all its values are in the range from -128 to 127.
pre-space
The number of decimal columns that are stored with leading spaces. In this case, each value contains a count for the number of leading spaces.
end-space
The number of columns that have a lot of trailing spaces. In this case, each value contains a count for the number of trailing spaces.
table-lookup
The column had only a small number of different values, which were converted to an ENUM before Huffman compression.
zero
The number of columns for which all values are zero.
Original trees
The initial number of Huffman trees.
After join
The number of distinct Huffman trees left after joining trees to save some header space.

After a table has been compressed, myisamchk -dvv prints additional information about each column:

Type
The column type. The value may contain any of the following descriptors:
- constant
  All rows have the same value.
- no endspace
  Do not store endspace.
- no endspace, not_always
  Do not store endspace and do not do endspace compression for all values.
- no endspace, no empty
  Do not store endspace. Do not store empty values.
- table-lookup
  The column was converted to an ENUM.
- zerofill(n)
  The most significant n bytes in the value are always 0 and are not stored.
- no zeros
  Do not store zeros.
- always zero
  Zero values are stored using one bit.
Huff tree
The number of the Huffman tree associated with the column.
Bits
The number of bits used in the Huffman tree.

After you run myisampack, you must run myisamchk to re-create any indexes. At this time, you can also sort the index blocks and create statistics needed for the MySQL optimizer to work more efficiently:

shell> myisamchk -rq --sort-index --analyze tbl_name.MYI

After you have installed the packed table into the MySQL database directory, you should execute mysqladmin flush-tables to force mysqld to start using the new table.

To unpack a packed table, use the --unpack option to myisamchk or isamchk.

8.3. mysql — The MySQL Command-Line Tool

8.3.1. Options
8.3.2. mysql Commands
8.3.3. Executing SQL Statements from a Text File
8.3.4. mysql Tips

mysql is a simple SQL shell (with GNU readline capabilities). It supports interactive and non-interactive use. When used interactively, query results are presented in an ASCII-table format. When used non-interactively (for example, as a filter), the result is presented in tab-separated format. The output format can be changed using command-line options.

If you have problems due to insufficient memory for large result sets, use the --quick option. This forces mysql to retrieve results from the server a row at a time rather than retrieving the entire result set and buffering it in memory before displaying it. This is done by using mysql_use_result() rather than mysql_store_result() to retrieve the result set.

Using mysql is very easy. Invoke it from the prompt of your command interpreter as follows:

shell> mysql db_name

Or:

shell> mysql --user=user_name --password=your_password db_name

Then type an SQL statement, end it with ‘;’, \g, or \G and press Enter.

You can run a script simply like this:

shell> mysql db_name < script.sql > output.tab

8.3.1. Options

mysql supports the following options:

--help, -?
Display a help message and exit.
--batch, -B
Print results using tab as the column separator, with each row on a new line. With this option, mysql does not use the history file.
--character-sets-dir=path
The directory where character sets are installed. See Section 5.10.1, “The Character Set Used for Data and Sorting”.
--compress, -C
Compress all information sent between the client and the server if both support compression.
--database=db_name, -D db_name
The database to use. This is useful mainly in an option file.
--debug[=debug_options], -# [debug_options]
Write a debugging log. The debug_options string often is 'd:t:o,file_name'. The default is 'd:t:o,/tmp/mysql.trace'.
--debug-info, -T
Print some debugging information when the program exits.
--default-character-set=charset
Use charset as the default character set. See Section 5.10.1, “The Character Set Used for Data and Sorting”.
--execute=statement, -e statement
Execute the statement and quit. The default output format is like that produced with --batch. See Section 4.3.1, “Using Options on the Command Line” for some examples.
--force, -f
Continue even if an SQL error occurs.
--host=host_name, -h host_name
Connect to the MySQL server on the given host.
--html, -H
Produce HTML output.
--ignore-space, -i
Ignore spaces after function names. The effect of this is described in the discussion for IGNORE_SPACE in Section 5.3.2, “The Server SQL Mode”.
--local-infile[={0|1}]
Enable or disable LOCAL capability for LOAD DATA INFILE. With no value, the option enables LOCAL. It may be given as --local-infile=0 or --local-infile=1 to explicitly disable or enable LOCAL. Enabling LOCAL has no effect if the server does not also support it.
--named-commands, -G
Named commands are enabled. Long format commands are allowed as well as shortened \* commands. For example, quit and \q both are recognized.
--no-auto-rehash, -A
No automatic rehashing. This option causes mysql to start faster, but you must issue the rehash command if you want to use table and column name completion.
--no-beep, -b
Do not beep when errors occur.
--no-named-commands, -g
Named commands are disabled. Use the \* form only, or use named commands only at the beginning of a line ending with a semicolon (‘;’). As of MySQL 3.23.22, mysql starts with this option enabled by default. However, even with this option, long-format commands still work from the first line.
--no-pager
Do not use a pager for displaying query output. Output paging is discussed further in Section 8.3.2, “mysql Commands”.
--no-tee
Do not copy output to a file. Tee files are discussed further in Section 8.3.2, “mysql Commands”.
--one-database, -O
Ignore statements except those for the default database named on the command line. This is useful for skipping updates to other databases in the binary log.
--pager[=command]
Use the given command for paging query output. If the command is omitted, the default pager is the value of your PAGER environment variable. Valid pagers are less, more, cat [> filename], and so forth. This option works only on Unix. It does not work in batch mode. Output paging is discussed further in Section 8.3.2, “mysql Commands”.
--password[=password], -p[password]
The password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, you are prompted for one. The password should be omitted on SysV-based UNIX systems, as the password may be displayed in the output of ps.
--port=port_num, -P port_num
The TCP/IP port number to use for the connection.
--prompt=format_str
Set the prompt to the specified format. The default is mysql>. The special sequences that the prompt can contain are described in Section 8.3.2, “mysql Commands”.
--protocol={TCP | SOCKET | PIPE | MEMORY}
The connection protocol to use.
--quick, -q
Do not cache each query result, print each row as it is received. This may slow down the server if the output is suspended. With this option, mysql does not use the history file.
--raw, -r
Write column values without escape conversion. Often used with the --batch option.
--reconnect
If the connection to the server is lost, automatically try to reconnect. A single reconnect attempt is made each time the connection is lost. To suppress reconnection behavior, use --skip-reconnect.
--safe-updates, --i-am-a-dummy, -U
Allow only those UPDATE and DELETE statements that specify rows to affect using key values. If you have set this option in an option file, you can override it by using --safe-updates on the command line. See Section 8.3.4, “mysql Tips” for more information about this option.
--secure-auth
Do not send passwords to the server in old (pre-4.1.1) format. This prevents connections except for servers that use the newer password format.
--show-warnings
Cause warnings to be shown after each statement if there are any. This option applies to interactive and batch mode.
--sigint-ignore
Ignore SIGINT signals (typically the result of typing Control-C).
--silent, -s
Silent mode. Produce less output. This option can be given multiple times to produce less and less output.
--skip-column-names, -N
Do not write column names in results.
--skip-line-numbers, -L
Do not write line numbers for errors. Useful when you want to compare result files that include error messages.
--socket=path, -S path
The socket file to use for the connection.
--table, -t
Display output in table format. This is the default for interactive use, but can be used to produce table output in batch mode.
--tee=file_name
Append a copy of output to the given file. This option does not work in batch mode. Tee files are discussed further in Section 8.3.2, “mysql Commands”.
--unbuffered, -n
Flush the buffer after each query.
--user=user_name, -u user_name
The MySQL username to use when connecting to the server.
--verbose, -v
Verbose mode. Produce more output. This option can be given multiple times to produce more and more output. (For example, -v -v -v produces the table output format even in batch mode.)
--version, -V
Display version information and exit.
--vertical, -E
Print the rows of query output vertically. Without this option, you can specify vertical output for individual statements by terminating them with \G.
--wait, -w
If the connection cannot be established, wait and retry instead of aborting.
--xml, -X
Produce XML output.

You can also set the following variables by using --var_name=value options:

connect_timeout
The number of seconds before connection timeout. (Default value is 0.)
max_allowed_packet
The maximum packet length to send to or receive from the server. (Default value is 16MB.)
max_join_size
The automatic limit for rows in a join when using --safe-updates. (Default value is 1,000,000.)
net_buffer_length
The buffer size for TCP/IP and socket communication. (Default value is 16KB.)
select_limit
The automatic limit for SELECT statements when using --safe-updates. (Default value is 1,000.)

It is also possible to set variables by using --set-variable=var_name=value or -O var_name=value syntax. This syntax is deprecated.

On Unix, the mysql client writes a record of executed statements to a history file. By default, the history file is named .mysql_history and is created in your home directory. To specify a different file, set the value of the MYSQL_HISTFILE environment variable.

If you do not want to maintain a history file, first remove .mysql_history if it exists, and then use either of the following techniques:

Set the MYSQL_HISTFILE variable to /dev/null. To cause this setting to take effect each time you log in, put the setting in one of your shell's startup files.
Create .mysql_history as a symbolic link to /dev/null:
```
shell> ln -s /dev/null $HOME/.mysql_history
```
You need do this only once.

8.3.2. mysql Commands

mysql sends SQL statements that you issue to the server to be executed. There is also a set of commands that mysql itself interprets. For a list of these commands, type help or \h at the mysql> prompt:

mysql> help

List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
?         (\?) Synonym for `help'.
clear     (\c) Clear command.
connect   (\r) Reconnect to the server. Optional arguments are db and host.
delimiter (\d) Set statement delimiter. NOTE: Takes the rest of the line as new delimiter.
edit      (\e) Edit command with $EDITOR.
ego       (\G) Send command to mysql server, display result vertically.
exit      (\q) Exit mysql. Same as quit.
go        (\g) Send command to mysql server.
help      (\h) Display this help.
nopager   (\n) Disable pager, print to stdout.
notee     (\t) Don't write into outfile.
pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
print     (\p) Print current command.
prompt    (\R) Change your mysql prompt.
quit      (\q) Quit mysql.
rehash    (\#) Rebuild completion hash.
source    (\.) Execute an SQL script file. Takes a file name as an argument.
status    (\s) Get status information from the server.
system    (\!) Execute a system shell command.
tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
use       (\u) Use another database. Takes database name as argument.
warnings  (\W) Show warnings after every statement.
nowarning (\w) Don't show warnings after every statement.

Each command has both a long and short form. The long form is not case sensitive; the short form is. The long form can be followed by an optional semicolon terminator, but the short form should not.

In the delimiter command, you should avoid the use of the backslash (‘\’) character because that is the escape character for MySQL.

The edit, nopager, pager, and system commands work only in Unix.

The status command provides some information about the connection and the server you are using. If you are running in --safe-updates mode, status also prints the values for the mysql variables that affect your queries.

To log queries and their output, use the tee command. All the data displayed on the screen is appended into a given file. This can be very useful for debugging purposes also. You can enable this feature on the command line with the --tee option, or interactively with the tee command. The tee file can be disabled interactively with the notee command. Executing tee again re-enables logging. Without a parameter, the previous file is used. Note that tee flushes query results to the file after each statement, just before mysql prints its next prompt.

Browsing or searching query results in interactive mode by using Unix programs such as less, more, or any other similar program is possible with the --pager option. If you specify no value for the option, mysql checks the value of the PAGER environment variable and sets the pager to that. Output paging can be enabled interactively with the pager command and disabled with nopager. The command takes an optional argument; if given, the paging program is set to that. With no argument, the pager is set to the pager that was set on the command line, or stdout if no pager was specified.

Output paging works only in Unix because it uses the popen() function, which does not exist on Windows. For Windows, the tee option can be used instead to save query output, although this is not as convenient as pager for browsing output in some situations.

A few tips about the pager command:

You can use it to write to a file and the results go only to the file:
```
mysql> pager cat > /tmp/log.txt
```
You can also pass any options for the program that you want to use as your pager:
```
mysql> pager less -n -i -S
```
In the preceding example, note the -S option. You may find it very useful for browsing wide query results. Sometimes a very wide result set is difficult to read on the screen. The -S option to less can make the result set much more readable because you can scroll it horizontally using the left-arrow and right-arrow keys. You can also use -S interactively within less to switch the horizontal-browse mode on and off. For more information, read the less manual page:
```
shell> man less
```
You can specify very complex pager commands for handling query output:
```
mysql> pager cat | tee /dr1/tmp/res.txt \
          | tee /dr2/tmp/res2.txt | less -n -i -S
```
In this example, the command would send query results to two files in two different directories on two different filesystems mounted on /dr1 and /dr2, yet still display the results onscreen via less.

You can also combine the tee and pager functions. Have a tee file enabled and pager set to less, and you are able to browse the results using the less program and still have everything appended into a file the same time. The difference between the Unix tee used with the pager command and the mysql built-in tee command is that the built-in tee works even if you do not have the Unix tee available. The built-in tee also logs everything that is printed on the screen, whereas the Unix tee used with pager does not log quite that much. Additionally, tee file logging can be turned on and off interactively from within mysql. This is useful when you want to log some queries to a file, but not others.

The default mysql> prompt can be reconfigured. The string for defining the prompt can contain the following special sequences:

Option	Description
`\v`	The server version
`\d`	The current database
`\h`	The server host
`\p`	The current TCP/IP port or socket file
`\u`	Your username
`\U`	Your full `user_name@host_name` account name
`\\`	A literal ‘`\`’ backslash character
`\n`	A newline character
`\t`	A tab character
`\`	A space (a space follows the backslash)
`\_`	A space
`\R`	The current time, in 24-hour military time (0-23)
`\r`	The current time, standard 12-hour time (1-12)
`\m`	Minutes of the current time
`\y`	The current year, two digits
`\Y`	The current year, four digits
`\D`	The full current date
`\s`	Seconds of the current time
`\w`	The current day of the week in three-letter format (Mon, Tue, ...)
`\P`	am/pm
`\o`	The current month in numeric format
`\O`	The current month in three-letter format (Jan, Feb, ...)
`\c`	A counter that increments for each statement you issue
`\S`	Semicolon
`\'`	Single quote
`\"`	Double quote

‘\’ followed by any other letter just becomes that letter.

If you specify the prompt command with no argument, mysql resets the prompt to the default of mysql>.

You can set the prompt in several ways:

Use an environment variable
You can set the MYSQL_PS1 environment variable to a prompt string. For example:
```
shell> export MYSQL_PS1="(\u@\h) [\d]> "
```
Use an option file
You can set the prompt option in the [mysql] group of any MySQL option file, such as /etc/my.cnf or the .my.cnf file in your home directory. For example:
```
[mysql]
prompt=(\\u@\\h) [\\d]>\\_
```
In this example, note that the backslashes are doubled. If you set the prompt using the prompt option in an option file, it is advisable to double the backslashes when using the special prompt options. There is some overlap in the set of allowable prompt options and the set of special escape sequences that are recognized in option files. (These sequences are listed in Section 4.3.2, “Using Option Files”.) The overlap may cause you problems if you use single backslashes. For example, \s is interpreted as a space rather than as the current seconds value. The following example shows how to define a prompt within an option file to include the current time in HH:MM:SS> format:
```
[mysql]
prompt="\\r:\\m:\\s> "
```
Use a command-line option
You can set the --prompt option on the command line to mysql. For example:
```
shell> mysql --prompt="(\u@\h) [\d]> "
(user@host) [database]>
```

Interactively

You can change your prompt interactively by using the prompt (or \R) command. For example:

mysql> prompt (\u@\h) [\d]>\_
PROMPT set to '(\u@\h) [\d]>\_'
(user@host) [database]>
(user@host) [database]> prompt
Returning to default PROMPT of mysql>
mysql>

8.3.3. Executing SQL Statements from a Text File

The mysql client typically is used interactively, like this:

shell> mysql db_name

However, it is also possible to put your SQL statements in a file and then tell mysql to read its input from that file. To do so, create a text file text_file that contains the statements you wish to execute. Then invoke mysql as shown here:

shell> mysql db_name < text_file

You can also start your text file with a USE db_name statement. In this case, it is unnecessary to specify the database name on the command line:

shell> mysql < text_file

If you are running mysql, you can execute an SQL script file using the source or \. command:

mysql> source filename
mysql> \. filename

Sometimes you may want your script to display progress information to the user; for this you can insert some lines like

SELECT '<info_to_display>' AS ' ';

which outputs <info_to_display>.

For more information about batch mode, see Section 3.5, “Using mysql in Batch Mode”.

8.3.4. mysql Tips

8.3.4.1. Displaying Query Results Vertically
8.3.4.2. Using the --safe-updates Option
8.3.4.3. Disabling mysql Auto-Reconnect

This section describes some techniques that can help you use mysql more effectively.

8.3.4.1. Displaying Query Results Vertically

Some query results are much more readable when displayed vertically, instead of in the usual horizontal table format. Queries can be displayed vertically by terminating the query with \G instead of a semicolon. For example, longer text values that include newlines often are much easier to read with vertical output:

mysql> SELECT * FROM mails WHERE LENGTH(txt) < 300 LIMIT 300,1\G
*************************** 1. row ***************************
  msg_nro: 3068
     date: 2000-03-01 23:29:50
time_zone: +0200
mail_from: Monty
    reply: monty@no.spam.com
  mail_to: "Thimble Smith" <tim@no.spam.com>
      sbj: UTF-8
      txt: >>>>> "Thimble" == Thimble Smith writes:

Thimble> Hi.  I think this is a good idea.  Is anyone familiar
Thimble> with UTF-8 or Unicode? Otherwise, I'll put this on my
Thimble> TODO list and see what happens.

Yes, please do that.

Regards,
Monty
     file: inbox-jani-1
     hash: 190402944
1 row in set (0.09 sec)

8.3.4.2. Using the `--safe-updates` Option

For beginners, a useful startup option is --safe-updates (or --i-am-a-dummy, which has the same effect). It is helpful for cases when you might have issued a DELETE FROM tbl_name statement but forgotten the WHERE clause. Normally, such a statement deletes all rows from the table. With --safe-updates, you can delete rows only by specifying the key values that identify them. This helps prevent accidents.

When you use the --safe-updates option, mysql issues the following statement when it connects to the MySQL server:

SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=1000, SQL_MAX_JOIN_SIZE=1000000;

See Section 13.5.3, “SET Syntax”.

The SET statement has the following effects:

You are not allowed to execute an UPDATE or DELETE statement unless you specify a key constraint in the WHERE clause or provide a LIMIT clause (or both). For example:
```
UPDATE tbl_name SET not_key_column=val WHERE key_column=val;

UPDATE tbl_name SET not_key_column=val LIMIT 1;
```
All large SELECT results are automatically limited to 1,000 rows unless the statement includes a LIMIT clause.
Multiple-table SELECT statements that probably need to examine more than 1,000,000 row combinations are aborted.

To specify limits other than 1,000 and 1,000,000, you can override the defaults by using --select_limit and --max_join_size options:

shell> mysql --safe-updates --select_limit=500 --max_join_size=10000

8.3.4.3. Disabling mysql Auto-Reconnect

If the mysql client loses its connection to the server while sending a query, it immediately and automatically tries to reconnect once to the server and send the query again. However, even if mysql succeeds in reconnecting, your first connection has ended and all your previous session objects and settings are lost: temporary tables, the autocommit mode, and user and session variables. This behavior may be dangerous for you, as in the following example where the server was shut down and restarted without you knowing it:

mysql> SET @a=1;
Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO t VALUES(@a);
ERROR 2006: MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    1
Current database: test

Query OK, 1 row affected (1.30 sec)

mysql> SELECT * FROM t;
+------+
| a    |
+------+
| NULL |
+------+
1 row in set (0.05 sec)

The @a user variable has been lost with the connection, and after the reconnection it is undefined. If it is important to have mysql terminate with an error if the connection has been lost, you can start the mysql client with the --skip-reconnect option.

8.4. mysqlaccess — Client for Checking Access Privileges

mysqlaccess is a diagnostic tool that Yves Carlier has provided for the MySQL distribution. It checks the access privileges for a hostname, username, and database combination. Note that mysqlaccess checks access using only the user, db, and host tables. It does not check table, column, or routine privileges specified in the tables_priv, columns_priv, or procs_priv tables.

Invoke mysqlaccess like this:

shell> mysqlaccess [host_name [user_name [db_name]]] [options]

mysqlaccess understands the following options:

--help, -?
Display a help message and exit.
--brief, -b
Generate reports in single-line tabular format.
--commit
Copy the new access privileges from the temporary tables to the original grant tables. The grant tables must be flushed for the new privileges to take effect. (For example, execute a mysqladmin reload command.)
--copy
Reload the temporary grant tables from original ones.
--db=db_name, -d db_name
Specify the database name.
--debug=N
Specify the debug level. N can be an integer from 0 to 3.
--host=host_name, -h host_name
The hostname to use in the access privileges.
--howto
Display some examples that show how to use mysqlaccess.
--old_server
Assume that the server is an old MySQL server (before MySQL 3.21) that does not yet know how to handle full WHERE clauses.
--password[=password], -p[password]
The password to use when connecting to the server. If you omit the password value following the --password or -p option on the command line, you are prompted for one.
--plan
Display suggestions and ideas for future releases.
--preview
Show the privilege differences after making changes to the temporary grant tables.
--relnotes
Display the release notes.
--rhost=host_name, -H host_name
Connect to the MySQL server on the given host.
--rollback
Undo the most recent changes to the temporary grant tables.
--spassword[=password], -P[password]
The password to use when connecting to the server as the superuser. If you omit the password value following the --password or -p option on the command line, you are prompted for one.
--superuser=user_name, -U user_name
Specify the username for connecting as the superuser.
--table, -t
Generate reports in table format.
--user=user_name, -u user_name
The hostname to use in the access privileges.
--version, -v
Display version information and exit.

If your MySQL distribution is installed in some non-standard location, you must change the location where mysqlaccess expects to find the mysql client. Edit the mysqlaccess script at approximately line 18. Search for a line that looks like this:

$MYSQL     = '/usr/local/bin/mysql';    # path to mysql executable

Change the path to reflect the location where mysql actually is stored on your system. If you do not do this, a Broken pipe error will occur when you run mysqlaccess.

8.5. mysqladmin — Client for Administering a MySQL Server

mysqladmin is a client for performing administrative operations. You can use it to check the server's configuration and current status, create and drop databases, and more.

Invoke mysqladmin like this:

shell> mysqladmin [options] command [command-options] [command [command-options]] ...

mysqladmin supports the following commands:

create db_name
Create a new database named db_name.
debug
Tell the server to write debug information to the error log.
drop db_name
Delete the database named db_name and all its tables.
extended-status
Display the server status variables and their values.
flush-hosts
Flush all information in the host cache.
flush-logs
Flush all logs.
flush-privileges
Reload the grant tables (same as reload).
flush-status
Clear status variables.
flush-tables
Flush all tables.
flush-threads
Flush the thread cache.
kill id,id,...
Kill server threads.
old-password new-password
This is like the password command but stores the password using the old (pre-4.1) password-hashing format. (See Section 5.7.9, “Password Hashing in MySQL 4.1”.)
password new-password
Set a new password. This changes the password to new-password for the account that you use with mysqladmin for connecting to the server.
If new-password contains spaces or other characters that are special to your command interpreter, you need to enclose it within quotes. On Windows, be sure to use double quotes rather than single quotes; single quotes are not stripped from the password, but rather are interpreted as part of the password. For example:
shell> mysqladmin password "my new password"
ping
Check whether the server is alive. The return status from mysqladmin is 0 if the server is running, 1 if it is not. This is 0 even in case of an error such as Access denied, because this means that the server is running but refused the connection, which is not the same as the server not running.
processlist
Show a list of active server threads. This is like the output of the SHOW PROCESSLIST statement. If the --verbose option is given, the output is like that of SHOW FULL PROCESSLIST. (See Section 13.5.4.16, “SHOW PROCESSLIST Syntax”.)
reload
Reload the grant tables.
refresh
Flush all tables and close and open log files.
shutdown
Stop the server.
start-slave
Start replication on a slave server.
status
Display a short server status message.
stop-slave
Stop replication on a slave server.
variables
Display the server system variables and their values.
version
Display version information from the server.

All commands can be shortened to any unique prefix. For example:

shell> mysqladmin proc stat
+----+-------+-----------+----+---------+------+-------+------------------+
| Id | User  | Host      | db | Command | Time | State | Info             |
+----+-------+-----------+----+---------+------+-------+------------------+
| 51 | monty | localhost |    | Query   | 0    |       | show processlist |
+----+-------+-----------+----+---------+------+-------+------------------+
Uptime: 1473624  Threads: 1  Questions: 39487  
Slow queries: 0  Opens: 541  Flush tables: 1  
Open tables: 19  Queries per second avg: 0.0268

The mysqladmin status command result displays the following values:

Uptime
The number of seconds the MySQL server has been running.
Threads
The number of active threads (clients).
Questions
The number of questions (queries) from clients since the server was started.
Slow queries
The number of queries that have taken more than long_query_time seconds. See Section 5.11.4, “The Slow Query Log”.
Opens
The number of tables the server has opened.
Flush tables
The number of flush ..., refresh, and reload commands the server has executed.
Open tables
The number of tables that currently are open.
Memory in use
The amount of memory allocated directly by mysqld code. This value is displayed only when MySQL has been compiled with --with-debug=full.
Maximum memory used
The maximum amount of memory allocated directly by mysqld code. This value is displayed only when MySQL has been compiled with --with-debug=full.

If you execute mysqladmin shutdown when connecting to a local server using a Unix socket file, mysqladmin waits until the server's process ID file has been removed, to ensure that the server has stopped properly.

mysqladmin supports the following options:

--help, -?
Display a help message and exit.
--character-sets-dir=path
The directory where character sets are installed. See Section 5.10.1, “The Character Set Used for Data and Sorting”.
--compress, -C
Compress all information sent between the client and the server if both support compression.
--count=num, -c num
The number of iterations to make. This works only with --sleep (-i).
--debug[=debug_options], -# [debug_options]
Write a debugging log. The debug_options string often is 'd:t:o,file_name'. The default is 'd:t:o,/tmp/mysqladmin.trace'.
--default-character-set=charset
Use charset as the default character set. See Section 5.10.1, “The Character Set Used for Data and Sorting”.
--force, -f
Do not ask for confirmation for the drop database command. With multiple commands, continue even if an error occurs.
--host=host_name, -h host_name
Connect to the MySQL server on the given host.
--password[=password], -p[password]
The password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, you are prompted for one.
--port=port_num, -P port_num
The TCP/IP port number to use for the connection.
--protocol={TCP | SOCKET | PIPE | MEMORY}
The connection protocol to use.
--relative, -r
Show the difference between the current and previous values when used with -i. Currently, this option works only with the extended-status command.
--silent, -s
Exit silently if a connection to the server cannot be established.
--sleep=delay, -i delay
Execute commands again and again, sleeping for delay seconds in between.
--socket=path, -S path
The socket file to use for the connection.
--user=user_name, -u user_name
The MySQL username to use when connecting to the server.
--verbose, -v
Verbose mode. Print out more information on what the program does.
--version, -V
Display version information and exit.
--vertical, -E
Print output vertically. This is similar to --relative, but prints output vertically.
--wait[=count], -w[count]
If the connection cannot be established, wait and retry instead of aborting. If an option value is given, it indicates the number of times to retry. The default is one time.

You can also set the following variables by using --var_name=value options:

connect_timeout
The maximum number of seconds before connection timeout. The default value is 43200 (12 hours).
shutdown_timeout
The maximum number of seconds to wait for shutdown. The default value is 3600 (1 hour).

It is also possible to set variables by using --set-variable=var_name=value or -O var_name=value syntax. However, this syntax is now deprecated, and should no longer be used.

8.6. mysqlbinlog — Utility for Processing Binary Log Files

The binary log files that the server generates are written in binary format. To examine these files in text format, use the mysqlbinlog utility.

Invoke mysqlbinlog like this:

shell> mysqlbinlog [options] log-file ...

For example, to display the contents of the binary log binlog.000003, use this command:

shell> mysqlbinlog binlog.0000003

The output includes all statements contained in binlog.000003, together with other information such as the time each statement took, the thread ID of the client that issued it, the timestamp when it was issued, and so forth.

Normally, you use mysqlbinlog to read binary log files directly and apply them to the local MySQL server. It is also possible to read binary logs from a remote server by using the --read-from-remote-server option.

When you read remote binary logs, the connection parameter options can be given to indicate how to connect to the server, but they are ignored unless you also specify the --read-from-remote-server option. These options are --host, --password, --port, --protocol, --socket, and --user.

You can also use mysqlbinlog to read relay log files written by a slave server in a replication setup. Relay logs have the same format as binary log files.

The binary log is discussed further in Section 5.11.3, “The Binary Log”.

mysqlbinlog supports the following options:

--help, -?
Display a help message and exit.
--database=db_name, -d db_name
List entries for just this database (local log only).
--force-read, -f
With this option, if mysqlbinlog reads a binary log event that it does not recognize, it prints a warning, ignores the event, and continues. Without this option, mysqlbinlog stops if it reads such an event.
--hexdump, -H
Display a hex dump of the log in comments. This output can be helpful for replication debugging. This option was added in MySQL 5.1.2.
--host=host_name, -h host_name
Get the binary log from the MySQL server on the given host.
--local-load=path, -l path
Prepare local temporary files for LOAD DATA INFILE in the specified directory.
--offset=N, -o N
Skip the first N entries.
--password[=password], -p[password]
The password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, you are prompted for one.
--port=port_num, -P port_num
The TCP/IP port number to use for connecting to a remote server.
--position=N, -j N
Deprecated, use --start-position instead.
--protocol={TCP | SOCKET | PIPE | MEMORY}
The connection protocol to use.
--read-from-remote-server, -R
Read the binary log from a MySQL server. Any connection parameter options are ignored unless this option is given as well. These options are --host, --password, --port, --protocol, --socket, and --user.
--result-file=name, -r name
Direct output to the given file.
--short-form, -s
Display only the statements contained in the log, without any extra information.
--socket=path, -S path
The socket file to use for the connection.
--start-datetime=datetime
Start reading the binary log at the first event having a datetime equal to or later than the datetime argument. The datetime value is relative to the local time zone on the machine where you run mysqlbinlog. The value should be in a format accepted for the DATETIME or TIMESTAMP data types. For example:
```
shell> mysqlbinlog --start-datetime="2004-12-25 11:25:56" binlog.000003
```
This option is useful for point-in-time recovery.
--stop-datetime=datetime
Stop reading the binary log at the first event having a datetime equal or posterior to the datetime argument. See the description of the --start-datetime option for information about the datetime value. It is useful for point-in-time recovery.
--start-position=N
Start reading the binary log at the first event having a position equal to the N argument.
--stop-position=N
Stop reading the binary log at the first event having a position equal or greater than the N argument.
--to-last-log, -t
Do not stop at the end of the requested binary log of the MySQL server, but rather continue printing until the end of the last binary log. If you send the output to the same MySQL server, this may lead to an endless loop. This option requires --read-from-remote-server.
--disable-log-bin, -D
Disable binary logging. This is useful for avoiding an endless loop if you use the --to-last-log option and are sending the output to the same MySQL server. This option also is useful when restoring after a crash to avoid duplication of the statements you have logged. Note: This option requires that you have the SUPER privilege.
--user=user_name, -u user_name
The MySQL username to use when connecting to a remote server.
--version, -V
Display version information and exit.

You can also set the following variable by using --var_name=value options:

open_files_limit