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
mysql supports the following options:
Print results using tab as the column separator, with each row on a new line. With this option, mysql doesn't use the history file.
The directory where character sets are installed. See the section called “The Character Set Used for Data and Sorting”.
Compress all information sent between the client and the server if both support compression.
The database to use. This is useful mainly in an option file.
Write a debugging log. The debug_options string often is 'd:t:o,file_name'. The default is 'd:t:o,/tmp/mysql.trace'.
Use charset as the default character set. See the section called “The Character Set Used for Data and Sorting”.
Execute the statement and quit. The default output format is like that produced with --batch.
Ignore spaces after function names. The effect of this is described in the discussion for IGNORE_SPACE in the section called “The Server SQL Mode”.
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 are enabled. Long format commands are allowed as well as shortened \* commands. For example, quit and \q both are recognized.
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.
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.
Do not use a pager for displaying query output. Output paging is discussed further in mysql Commands.
Do not copy output to a file. Tee files are discussed further in mysql Commands.
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.
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 mysql Commands.
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 no password is given on the command line, you will be prompted for one.
Set the prompt to the specified format. The default is mysql>. The special sequences that the prompt can contain are described in mysql Commands.
Don't 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 doesn't use the history file.
Write column values without escape conversion. Often used with the --batch option.
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. New in MySQL 4.1.0.
Allow only UPDATE and DELETE statements that specify rows to affect using key values. If you have this option in an option file, you can override it by using --safe-updates on the command line. See mysql Tips for more information about this option.
Ignore SIGINT signals (typically the result of typing Control-C). This option was added in MySQL 4.1.6.
Silent mode. Produce less output. This option can be given multiple times to produce less and less output.
Don't write line numbers for errors. Useful when you want to compare result files that include error messages.
Display output in table format. This is the default for interactive use, but can be used to produce table output in batch mode.
Append a copy of output to the given file. This option does not work in batch mode. Tee files are discussed further in mysql Commands.
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.)
Print the rows of query output vertically. Without this option, you can specify vertical output for individual statements by terminating them with \G.
If the connection cannot be established, wait and retry instead of aborting.
You can also set the following variables by using --var_name=value options:
The number of seconds before connection timeout. (Default value is 0.)
The maximum packet length to send to or receive from the server. (Default value is 16MB.)
The automatic limit for rows in a join when using --safe-updates. (Default value is 1,000,000.)
The buffer size for TCP/IP and socket communication. (Default value is 16KB.)
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. However, this syntax is deprecated as of MySQL 4.0.
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.
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
MySQL commands:
? (\h) Synonym for `help'.
clear (\c) Clear command.
connect (\r) Reconnect to the server.
Optional arguments are db and host.
delimiter (\d) Set query 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.
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.
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 will be 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 will be 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 now 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 doesn't 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 will 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 will be 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 don't 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 doesn't 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.
From MySQL 4.0.2 on, 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 host |
| \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 the section called “Using Option Files”.) The overlap may cause you problems if you use single backslashes. For example, \s will be 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>
The mysql client typically is used interactively, like this:
shell> mysql db_name
However, it's 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 already 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 will output <info_to_display>.
For more information about batch mode, see the section called “Using mysql in Batch Mode”.
This section describes some techniques that can help you use mysql more effectively.
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)
For beginners, a useful startup option is --safe-updates (or --i-am-a-dummy, which has the same effect). This option was introduced in MySQL 3.23.11. 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 will delete 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 SET.
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=# WHERE key_column=#; UPDATE tbl_name SET not_key_column=# 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 will 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
If the mysql client loses its connection to the server while sending a query, it will immediately and automatically try 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.