mysql - the MySQL command-line tool at Linux.org

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MYSQL(1) MySQL Database System MYSQL(1)

NAME
mysql - the MySQL command-line tool

SYNOPSIS
mysql [options] db_name

DESCRIPTION
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
mysql supports the following options, which can be specified on the command line or in the [mysql] and
[client] option file groups. mysql also supports the options for processing option files described at
Section 4.2.3.3.1, “Command-Line Options that Affect Option-File Handling”.

· --help, -?, -I

Display a help message and exit.

· --auto-rehash

Enable automatic rehashing. This option is on by default, which enables database, table, and column name
completion. Use --disable-auto-rehash to disable rehashing. That causes mysql to start faster, but you
must issue the rehash command if you want to use name completion.

To complete a name, enter the first part and press Tab. If the name is unambiguous, mysql completes it.
Otherwise, you can press Tab again to see the possible names that begin with what you have typed so far.
Completion does not occur if there is no default database.

· --batch, -B

Write column names in results.

· --column-type-info, -m

Display result set metadata. This option was added in MySQL 5.1.14. (Before that, use --debug-info.) The
-m short option was added in MySQL 5.1.21.

· --comments, -c

Whether to preserve comments in statements sent to the server. The default is --skip-comments (discard
comments), enable with --comments (preserve comments). This option was added in MySQL 5.1.23.

· --compress, -C

Compress all information sent between the client and the server if both support compression.

· --connect-timeout=seconds

Set the number of seconds before connection timeout. (Default value is 0.)

· --database=db_name, -D db_name

The database to use. This is useful primarily in an option file.

· --debug[=debug_options], -# [debug_options]

Write a debugging log. A typical debug_options string is ´d:t:o,file_name´. The default is
´d:t:o,/tmp/mysql.trace´.

· --debug-check

Print some debugging information when the program exits. This option was added in MySQL 5.1.21.

· --debug-info, -T

Before MySQL 5.1.14, this option prints debugging information and memory and CPU usage statistics when the
program exits, and also causes display of result set metadata during execution. As of MySQL 5.1.14, use
--column-type-info to display result set metadata.

· --default-character-set=charset_name

Use charset_name as the default character set for the client and connection.

A common issue that can occur when the operating system uses utf8 or another multi-byte character set is
that output from the mysql client is formatted incorrectly, due to the fact that the MySQL client uses the
latin1 character set by default. You can usually fix such issues by using this option to force the client
to use the system character set instead.

See Section 9.5, “Character Set Configuration”, for more information.

· --defaults-file=filename

Set filename as the file to read default options from, override global defaults files. Must be given as
first option.
Disable named commands. Use the \* form only, or use named commands only at the beginning of a line ending
with a semicolon (“;”). mysql starts with this option enabled by default. However, even with this option,
long-format commands still work from the first line. See the section called “MYSQL COMMANDS”.

· --execute=statement, -e statement

Execute the statement and quit. The default output format is like that produced with --batch. See
Section 4.2.3.1, “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-spaces, -i

Ignore spaces after function names. The effect of this is described in the discussion for the IGNORE_SPACE
SQL mode (see Section 5.1.8, “Server SQL Modes”).

· --line-numbers

Write line numbers for errors. Disable this with --skip-line-numbers.

· --local-infile[={0|1}]

Enable or disable LOCAL capability for LOAD DATA INFILE. With no value, the option enables LOCAL. The
option 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.

· --max-allowed-packet=num

Set the maximum packet length to send to or receive from the server. (Default value is 16MB.)

· --max-join-size=num

Set the automatic limit for rows in a join when using --safe-updates. (Default value is 1,000,000.)

· --named-commands, -G

Enable named mysql commands. Long-format commands are allowed, not just short-format commands. For
example, quit and \q both are recognized. Use --skip-named-commands to disable named commands. See the
section called “MYSQL COMMANDS”.

· --net-buffer-lenght=size

Set the buffer size for TCP/IP and socket communication. (Default value is 16KB.)

· --no-named-commands, -g

Deprecated, use --disable-named-commands instead. --no-named-commands is removed in MySQL 5.5.

· --no-pager

Deprecated form of --skip-pager. See the --pager option. --no-pager is removed in MySQL 5.5.

· --no-tee

Deprecated form of --skip-tee. See the --tee option. --no-tee is removed in MySQL 5.5.

· --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 and only in interactive mode. To disable paging, use --skip-pager. the section
called “MYSQL COMMANDS”, discusses output paging further.

· --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, mysql prompts for one.

Specifying a password on the command line should be considered insecure. See Section 5.3.2.2, “End-User
Guidelines for Password Security”. You can use an option file to avoid giving the password on the command
line.

· --pipe, -W

On Windows, connect to the server via a named pipe. This option applies only if the server supports
named-pipe connections.

· --port=port_num, -P port_num

The TCP/IP port number to use for the connection.

· --print-defaults

Print the program argument list and exit. This must be given as the first argument.

· --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 the section called “MYSQL COMMANDS”.

· --protocol={TCP|SOCKET|PIPE|MEMORY}

For nontabular output (such as is produced in batch mode or when the --batch or --silent option is given),
special characters are escaped in the output so they can be identified easily. Newline, tab, NUL, and
backslash are written as \n, \t, \0, and \\. The --raw option disables this character escaping.

The following example demonstrates tabular versus nontabular output and the use of raw mode to disable
escaping:

% mysql
mysql> SELECT CHAR(92);
+----------+
| CHAR(92) |
+----------+
| \ |
+----------+
% mysql -s
mysql> SELECT CHAR(92);
CHAR(92)
\\
% mysql -s -r
mysql> SELECT CHAR(92);
CHAR(92)
\

· --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 which rows to modify by 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 the section called “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.

· --select-limit=limit

Set automatic limit for SELECT when using --safe-updates. (Default value is 1,000.)

· --server-arg=name

Send name as a parameter to the embedded server.

· --show-warnings

Cause warnings to be shown after each statement if there are any. This option applies to interactive and
batch mode.

· --sigint-ignore

· --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

For connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to
use.

· --ssl*

Options that begin with --ssl specify whether to connect to the server via SSL and indicate where to find
SSL keys and certificates. See Section 5.5.6.3, “SSL Command Options”.

· --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 works only in interactive mode. the section called
“MYSQL COMMANDS”, discusses tee files further.

· --unbuffered, -n

Flush the buffer after each query.

· --user=user_name, -u user_name

The MySQL user name to use when connecting to the server.

· --verbose, -v

Verbose mode. Produce more output about what the program does. This option can be given multiple times to
produce more and more output. (For example, -v -v -v produces table output format even in batch mode.)

· --version, -V

Display version information and exit.

· --vertical, -E

Print query output rows vertically (one line per column value). Without this option, you can specify
vertical output for individual statements by terminating them with \G.

· --wait, -w

Beginning with MySQL 5.1.12, the output when --xml is used with mysql matches that of mysqldump --xml. See
mysqldump(1) for details.

Beginning with MySQL 5.1.18, the XML output also uses an XML namespace, as shown here:

shell> mysql --xml -uroot -e "SHOW VARIABLES LIKE ´version%´"
<?xml version="1.0"?>
<resultset statement="SHOW VARIABLES LIKE ´version%´" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<row>
<field name="Variable_name">version</field>
<field name="Value">5.0.40-debug</field>
</row>
<row>
<field name="Variable_name">version_comment</field>
<field name="Value">Source distribution</field>
</row>
<row>
<field name="Variable_name">version_compile_machine</field>
<field name="Value">i686</field>
</row>
<row>
<field name="Variable_name">version_compile_os</field>
<field name="Value">suse-linux-gnu</field>
</row>
</resultset>

(See Bug#25946[1].)

You can also set the following variables by using --var_name=value. The --set-variable format is deprecated
and is removed in MySQL 5.5.

· 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.)

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
· 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 COMMANDS
mysql sends each SQL statement 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.
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.
charset (\C) Switch to another charset. Might be needed for processing
binlog with multi-byte charsets.
warnings (\W) Show warnings after every statement.
nowarning (\w) Don´t show warnings after every statement.
For server side help, type ´help contents´

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 use of short-form commands within multi-line /* ... */ comments is not supported.

· help [arg], \h [arg], \? [arg], ? [arg]

Display a help message listing the available mysql commands.

If you provide an argument to the help command, mysql uses it as a search string to access server-side
help from the contents of the MySQL Reference Manual. For more information, see the section called “MYSQL
SERVER-SIDE HELP”.

· connect [db_name host_name]], \r [db_name host_name]]

Reconnect to the server. The optional database name and host name arguments may be given to specify the
default database or the host where the server is running. If omitted, the current values are used.

· delimiter str, \d str

Change the string that mysql interprets as the separator between SQL statements. The default is the
semicolon character (“;”).

The delimiter can be specified as an unquoted or quoted argument. Quoting can be done with either single
quote (´) or douple quote (") characters. To include a quote within a quoted string, either quote the
string with the other quote character or escape the quote with a backslash (“\”) character. Backslash
should be avoided outside of quoted strings because it is the escape character for MySQL. For an unquoted
argument, the delmiter is read up to the first space or end of line. For a quoted argument, the delimiter
is read up to the matching quote on the line.

When the delimiter recognized by mysql is set to something other than the default of “;”, instances of
that character are sent to the server without interpretation. However, the server itself still interprets
“;” as a statement delimiter and processes statements accordingly. This behavior on the server side comes
into play for multiple-statement execution (see Section 21.9.12, “C API Support for Multiple Statement
Execution”), and for parsing the body of stored procedures and functions, triggers, and events (see
Section 19.1, “Defining Stored Programs”).

· edit, \e

Edit the current input statement. mysql checks the values of the EDITOR and VISUAL environment variables
to determine which editor to use. The default editor is vi if neither variable is set.

The edit command works only in Unix.

· ego, \G

Send the current statement to the server to be executed and display the result using vertical format.

· exit, \q

Exit mysql.

· go, \g

Send the current statement to the server to be executed.

· nopager, \n

Disable output paging. See the description for pager.

The nopager command works only in Unix.

· notee, \t

Disable output copying to the tee file. See the description for tee.

· nowarning, \w

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 it is not as convenient as
pager for browsing output in some situations.

· print, \p

Print the current input statement without executing it.

· prompt [str], \R [str]

Reconfigure the mysql prompt to the given string. The special character sequences that can be used in the
prompt are described later in this section.

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

· quit, \q

Exit mysql.

· rehash, \#

Rebuild the completion hash that enables database, table, and column name completion while you are
entering statements. (See the description for the --auto-rehash option.)

· source file_name, \. file_name

Read the named file and executes the statements contained therein. On Windows, you can specify path name
separators as / or \\.

· status, \s

Provide status 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.

· system command, \! command

Execute the given command using your default command interpreter.

The system command works only in Unix.

· tee [file_name], \T [file_name]

By using the --tee option when you invoke mysql, you can log statements and their output. All the data
displayed on the screen is appended into a given file. This can be very useful for debugging purposes
also. mysql flushes results to the file after each statement, just before it prints its next prompt. Tee
functionality works only in interactive mode.

You can enable this feature interactively with the tee command. Without a parameter, the previous file is
used. The tee file can be disabled with the notee command. Executing tee again re-enables logging.

· use db_name, \u db_name

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

· The -F and -X options may be used with less to cause it to exit if output fits on one screen, which is
convenient when no scrolling is necessary:

mysql> pager less -n -i -S -F -X

· 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 file systems 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 prompt command reconfigures the default mysql> prompt. The string for defining the prompt can contain the
following special sequences.

┌───────┬─────────────────────────────────────────┐
│Option │ Description │
├───────┼─────────────────────────────────────────┤
│\c │ A counter that increments for each │
│ │ statement you issue │
├───────┼─────────────────────────────────────────┤
│\D │ The full current date │
├───────┼─────────────────────────────────────────┤
│\d │ The default database │
├───────┼─────────────────────────────────────────┤
│\h │ The server host │
├───────┼─────────────────────────────────────────┤
│\l │ The current delimiter (new in 5.1.12) │
├───────┼─────────────────────────────────────────┤
│\m │ Minutes of the current time │
├───────┼─────────────────────────────────────────┤
│\n │ A newline character │
├───────┼─────────────────────────────────────────┤
│\r │ The current time, standard 12-hour time │
│ │ (1–12) │
├───────┼─────────────────────────────────────────┤
│\S │ Semicolon │
├───────┼─────────────────────────────────────────┤
│\s │ Seconds of the current time │
├───────┼─────────────────────────────────────────┤
│\t │ A tab character │
├───────┼─────────────────────────────────────────┤
│\U │ │
│ │ Your full user_name@host_name │
│ │ account name │
├───────┼─────────────────────────────────────────┤
│\u │ Your user name │
├───────┼─────────────────────────────────────────┤
│\v │ The server version │
├───────┼─────────────────────────────────────────┤
│\w │ The current day of the week in │
│ │ three-letter format (Mon, Tue, ...) │
├───────┼─────────────────────────────────────────┤
│\Y │ The current year, four digits │
├───────┼─────────────────────────────────────────┤
│\y │ The current year, two digits │
├───────┼─────────────────────────────────────────┤
│\_ │ A space │
├───────┼─────────────────────────────────────────┤
│\ │ A space (a space follows the backslash) │
├───────┼─────────────────────────────────────────┤
│\´ │ Single quote │
├───────┼─────────────────────────────────────────┤
│\" │ Double quote │
├───────┼─────────────────────────────────────────┤
│\\ │ A literal “\” backslash character │
├───────┼─────────────────────────────────────────┤
│\x │ │
│ │ x, for any “x” not listed above │
└───────┴─────────────────────────────────────────┘

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 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]>

· 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]

· Set the prompt 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>

MYSQL SERVER-SIDE HELP
mysql> help search_string

If you provide an argument to the help command, mysql uses it as a search string to access server-side help
from the contents of the MySQL Reference Manual. The proper operation of this command requires that the help
tables in the mysql database be initialized with help topic information (see Section 5.1.9, “Server-Side
Help”).

If there is no match for the search string, the search fails:

mysql> help me
Nothing found
Please try to run ´help contents´ for a list of all accessible topics

Use help contents to see a list of the help categories:

mysql> help contents
You asked for help about help category: "Contents"
For more information, type ´help <item>´, where <item> is one of the
following categories:
Account Management
Administration
Data Definition
Data Manipulation
Data Types
Functions
Functions and Modifiers for Use with GROUP BY
Geographic Features
Language Structure
Plugins
Storage Engines
Stored Routines
Table Maintenance
Transactions
Triggers

If the search string matches multiple items, mysql shows a list of matching topics:

mysql> help logs
Many help items for your request exist.
To make a more specific request, please type ´help <item>´,
where <item> is one of the following topics:
SHOW

Lists the binary log files on the server. This statement is used as
part of the procedure described in [purge-binary-logs], that shows how
to determine which logs can be purged.
mysql> SHOW BINARY LOGS;
+---------------+-----------+
| Log_name | File_size |
+---------------+-----------+
| binlog.000015 | 724935 |
| binlog.000016 | 733481 |
+---------------+-----------+

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

If you place a USE db_name statement as the first statement in the file, 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 command or \. command:

mysql> source file_name
mysql> \. file_name

Sometimes you may want your script to display progress information to the user. For this you can insert
statements like this:

SELECT ´<info_to_display>´ AS ´ ´;

The statement shown outputs <info_to_display>.

You can also invoke mysql with the --verbose option, which causes each statement to be displayed before the
result that it produces.

As of MySQL 5.1.23, mysql ignores Unicode byte order mark (BOM) characters at the beginning of input files.
Previously, it read them and sent them to the server, resulting in a syntax error. Presence of a BOM does not
cause mysql to change its default character set. To do that, invoke mysql with an option such as
--default-character-set=utf8.

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

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

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;

See Section 5.1.5, “Session System Variables”.

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

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.

For more information about auto-reconnect and its effect on state information when a reconnection occurs, see
Section 21.9.11, “Controlling Automatic Reconnection Behavior”.

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU
General Public License as published by the Free Software Foundation; version 2 of the License.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for more details.

You should have received a copy of the GNU General Public License along with the program; if not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see
http://www.gnu.org/licenses/.

NOTES
1. Bug#25946
http://bugs.mysql.com/bug.php?id=25946

SEE ALSO
For more information, please refer to the MySQL Reference Manual, which may already be installed locally and
which is also available online at http://dev.mysql.com/doc/.

AUTHOR
Sun Microsystems, Inc. (http://www.mysql.com/).

MySQL 5.1 04/06/2010 MYSQL(1)