About the mysql Command-line Client

mysql is a simple SQL shell (with GNU readline capabilities). It supports interactive and noninteractive use. When used interactively, query results are presented in an ASCII-table format. When used noninteractively (for example, as a filter), the result is presented in tab-separated format. The output format can be changed using command 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 returning the result set using the mysql_use_result() C API function in the client/server library rather than mysql_store_result().

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.

As of MySQL 5.1.10, typing Control-C causes mysql to attempt to kill the current statement. If this cannot be done, or Control-C is typed again before the statement is killed, mysql exits. Previously, Control-C caused mysql to exit in all cases.

You can execute SQL statements in a script file (batch file) like this:

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

mysql Options

Options can be specified on the command line or in the [mysql] and [client] option file groups of a my.cnf file. The full list of supported options can be obtained with:

shell> mysql --verbose --help

In MariaDB 10.0.2 the output of the above command is:

shell> mysql --verbose --help mysql Ver 15.1 Distrib 10.0.2-MariaDB, for debian-linux-gnu (i686) using readline 5.1 Copyright © 2000, 2013, Oracle, Monty Program Ab and others.

Usage: mysql [OPTIONS] [database] -?, --help Display this help and exit. -I, --help Synonym for -? --abort-source-on-error Abort 'source filename' operations in case of errors --auto-rehash Enable automatic rehashing. One doesn't need to use 'rehash' to get table and field completion, but startup and reconnecting may take a longer time. Disable with --disable-auto-rehash. (Defaults to on; use --skip-auto-rehash to disable.) -A, --no-auto-rehash No automatic rehashing. One has to use 'rehash' to get table and field completion. This gives a quicker start of mysql and disables rehashing on reconnect. --auto-vertical-output Automatically switch to vertical output mode if the result is wider than the terminal width. -B, --batch Don't use history file. Disable interactive behavior. (Enables --silent.) --character-sets-dir=name Directory for character set files. --column-type-info Display column type information. -c, --comments Preserve comments. Send comments to the server. The default is --skip-comments (discard comments), enable with --comments. -C, --compress Use compression in server/client protocol. -#, --debug[=#] This is a non-debug version. Catch this and exit. --debug-check Check memory and open file usage at exit. -T, --debug-info Print some debug info at exit. -D, --database=name Database to use. --default-character-set=name Set the default character set. --delimiter=name Delimiter to be used. -e, --execute=name Execute command and quit. (Disables --force and history file.) -E, --vertical Print the output of a query (rows) vertically. -f, --force Continue even if we get an SQL error. Sets abort-source-on-error to 0 -G, --named-commands Enable named commands. Named commands mean this program's internal commands; see mysql> help . When enabled, the named commands can be used from any line of the query, otherwise only from the first line, before an enter. Disable with --disable-named-commands. This option is disabled by default. -i, --ignore-spaces Ignore space after function names. --init-command=name SQL Command to execute when connecting to MySQL server. Will automatically be re-executed when reconnecting. --local-infile Enable/disable LOAD DATA LOCAL INFILE. -b, --no-beep Turn off beep on error. -h, --host=name Connect to host. -H, --html Produce HTML output. -X, --xml Produce XML output. --line-numbers Write line numbers for errors. (Defaults to on; use --skip-line-numbers to disable.) -L, --skip-line-numbers Don't write line number for errors. -n, --unbuffered Flush buffer after each query. --column-names Write column names in results. (Defaults to on; use --skip-column-names to disable.) -N, --skip-column-names Don't write column names in results. --sigint-ignore Ignore SIGINT (CTRL-C). -o, --one-database Ignore statements except those that occur while the default database is the one named at the command line. --pager[=name] Pager to use to display results. If you don't supply an option, the default pager is taken from your ENV variable PAGER. Valid pagers are less, more, cat [> filename], etc. See interactive help (\h) also. This option does not work in batch mode. Disable with --disable-pager. This option is disabled by default. -p, --password[=name] Password to use when connecting to server. If password is not given it's asked from the tty. -P, --port=# Port number to use for connection or 0 for default to, in order of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default (3306). --progress-reports Get progress reports for long running commands (like ALTER TABLE) (Defaults to on; use --skip-progress-reports to disable.) --prompt=name Set the mysql prompt to this value. --protocol=name The protocol to use for connection (tcp, socket, pipe, memory). -q, --quick Don't cache result, print it row by row. This may slow down the server if the output is suspended. Doesn't use history file. -r, --raw Write fields without conversion. Used with --batch. --reconnect Reconnect if the connection is lost. Disable with --disable-reconnect. This option is enabled by default. (Defaults to on; use --skip-reconnect to disable.) -s, --silent Be more silent. Print results with a tab as separator, each row on new line. -S, --socket=name The socket file to use for connection. --ssl Enable SSL for connection (automatically enabled with other flags). --ssl-ca=name CA file in PEM format (check OpenSSL docs, implies --ssl). --ssl-capath=name CA directory (check OpenSSL docs, implies --ssl). --ssl-cert=name X509 cert in PEM format (implies --ssl). --ssl-cipher=name SSL cipher to use (implies --ssl). --ssl-key=name X509 key in PEM format (implies --ssl). --ssl-crl=name Certificate revocation list (implies --ssl). --ssl-crlpath=name Certificate revocation list path (implies --ssl). --ssl-verify-server-cert Verify server's "Common Name" in its cert against hostname used when connecting. This option is disabled by default. -t, --table Output in table format. --tee=name Append everything into outfile. See interactive help (\h) also. Does not work in batch mode. Disable with --disable-tee. This option is disabled by default. -u, --user=name User for login if not current user. -U, --safe-updates Only allow UPDATE and DELETE that uses keys. -U, --i-am-a-dummy Synonym for option --safe-updates, -U. -v, --verbose Write more. (-v -v -v gives the table output format). -V, --version Output version information and exit. -w, --wait Wait and retry if connection is down. --connect-timeout=# Number of seconds before connection timeout. --max-allowed-packet=# The maximum packet length to send to or receive from server. --net-buffer-length=# The buffer size for TCP/IP and socket communication. --select-limit=# Automatic limit for SELECT when using --safe-updates. --max-join-size=# Automatic limit for rows in a join when using --safe-updates. --secure-auth Refuse client connecting to server if it uses old (pre-4.1.1) protocol. --server-arg=name Send embedded server this as a parameter. --show-warnings Show warnings after every statement. --plugin-dir=name Directory for client-side plugins. --default-auth=name Default authentication client-side plugin to use.

Default options are read from the following files in the given order: /etc/my.cnf /etc/mysql/my.cnf /.my.cnf The following groups are read: mysql client client-server client-mariadb The following options may be given as the first argument: --print-defaults Print the program argument list and exit. --no-defaults Don't read default options from any option file. --defaults-file=# Only read default options from the given file #. --defaults-extra-file=# Read this file after the global files are read.

Variables (--variable-name=value) and boolean options {FALSE|TRUE} Value (after reading options) --------------------------------- ---------------------------------------- abort-source-on-error FALSE auto-rehash TRUE auto-vertical-output FALSE character-sets-dir (No default value) column-type-info FALSE comments FALSE compress FALSE debug-check FALSE debug-info FALSE database (No default value) default-character-set auto delimiter ; vertical FALSE force FALSE named-commands FALSE ignore-spaces FALSE init-command (No default value) local-infile FALSE no-beep FALSE host (No default value) html FALSE xml FALSE line-numbers TRUE unbuffered FALSE column-names TRUE sigint-ignore FALSE port 3306 progress-reports TRUE prompt \N [\d]> quick FALSE raw FALSE reconnect TRUE socket /var/run/mysqld/mysqld.sock ssl FALSE ssl-ca (No default value) ssl-capath (No default value) ssl-cert (No default value) ssl-cipher (No default value) ssl-key (No default value) ssl-crl (No default value) ssl-crlpath (No default value) ssl-verify-server-cert FALSE table FALSE user (No default value) safe-updates FALSE i-am-a-dummy FALSE connect-timeout 0 max-allowed-packet 16777216 net-buffer-length 16384 select-limit 1000 max-join-size 1000000 secure-auth FALSE show-warnings FALSE plugin-dir (No default value) default-auth (No default value)

The output you get when running the above may differ depending on any customizations you may have in your local my.cnf file. See Configuring MariaDB with my.cnf.

The mysql_history File

On Unix, the mysql client writes a record of executed statements to a history file. By default, this 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.

The .mysql_history should be protected with a restrictive access mode because sensitive information might be written to it, such as the text of SQL statements that contain passwords. See Section 5.3.2.2, “End-User Guidelines for Password Security”.

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 Tips

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

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)

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;

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;
  • The server limits all large SELECT results to 1,000 rows unless the statement includes a LIMIT clause.
  • The server aborts multiple-table SELECT statements that probably need to examine more than 1,000,000 row combinations.

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

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

Disabling mysql Auto-Reconnect

If the mysql client loses its connection to the server while sending a statement, it immediately and automatically tries to reconnect once to the server and send the statement 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-defined and session variables. Also, any current transaction rolls back. This behavior may be dangerous for you, as in the following example where the server was shut down and restarted between the first and second statements 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.

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