MYSQL(1) | MariaDB Database System | MYSQL(1) |
NAME¶
mysql - the MariaDB command-line toolSYNOPSIS¶
mysql [options]
db_name
DESCRIPTION¶
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 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
shell> mysql --user=user_name --password=your_password db_name
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], [client], [client-server] or [client-mariadb] option file groups. mysql also supports the options for processing option files.•--help, -?, -I
Display a help message and exit.
•--abort-source-on-error
Abort 'source filename' operations in case of errors.
•--auto-rehash
Enable automatic rehashing. This option is on by default, which enables
database, table, and column name completion. Use --disable-auto-rehash,
--no-auto-rehash, or --skip-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.
•--auto-vertical-output
Automatically switch to vertical output mode if the result is wider than the
terminal width.
•--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.
Batch mode results in nontabular output format and escaping of special
characters. Escaping may be disabled by using raw mode; see the description
for the --raw option.
•--binary-mode
By default, ASCII '\0' is disallowed and '\r\n' is translated to '\n'. This
switch turns off both features, and also turns off parsing of all client
commands except \C and DELIMITER, in non-interactive mode (for input piped to
mysql or loaded using the 'source' command). This is necessary when processing
output from mysqlbinlog that may contain blobs.
•--character-sets-dir=path
The directory where character sets are installed.
•--column-names
Write column names in results.
•--column-type-info, -m
Display result set metadata.
•--comments, -c
Whether to preserve comments in statements sent to the server. The default is
--skip-comments (discard comments), enable with --comments (preserve
comments).
•--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.
•--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.
•--debug-info, -T
Prints debugging information and memory and CPU usage statistics when the
program exits.
•--default-auth=name
Default authentication client-side plugin to use.
•--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 MariaDB 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.
•--defaults-extra-file=filename
Set filename as the file to read default options from after the
global defaults files has been read. Must be given as first option.
•--defaults-file=filename
Set filename as the file to read default options from, override
global defaults files. Must be given as first option.
•--defaults-group-suffix=suffix
In addition to the groups named on the command line, read groups that have the
given suffix.
•--delimiter=str
Set the statement delimiter. The default is the semicolon character
(“;”).
•--disable-named-commands
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. Disables --force and history file. The
default output format is like that produced with --batch.
•--force, -f
Continue even if an SQL error occurs. Sets --abort-source-on-error to
0.
•--host=host_name, -h
host_name
Connect to the MariaDB server on the given host.
•--html, -H
Produce HTML output.
•--ignore-spaces, -i
Ignore spaces after function names. Allows one to have spaces (including tab
characters and new line characters) between function name and '('. The
drawback is that this causes built in functions to become reserved
words.
•--init-command=str
SQL Command to execute when connecting to the MariaDB server. Will automatically
be re-executed when reconnecting.
•--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, largest 1GB.)
•--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”. Disabled by default.
••--net-buffer-lenght=size
Set the buffer size for TCP/IP and socket communication. (Default value is
16KB.)
•--no-auto-rehash, -A
This has the same effect as --skip-auto-rehash. See the description for
--auto-rehash.
•--no-beep, -b
Do not beep when errors occur.
•--no-defaults
Do not read default options from any option file. This must be given as the
first argument.
•--one-database, -o
Ignore statements except those those that occur while the default database is
the one named on the command line. This filtering is limited, and based only
on USE statements. 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. 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.
•--plugin-dir=dir_name
Directory for client-side plugins.
•--port=port_num, -P
port_num
The TCP/IP port number to use for the connection or 0 for default to, in order
of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default
(3306).
•--print-defaults
Print the program argument list and exit. This must be given as the first
argument.
•--progress-reports
Get progress reports for long running commands (such as ALTER TABLE). (Defaults
to on; use --skip-progress-reports to disable.)
•--prompt=format_str
Set the prompt to the specified format. The special sequences that the prompt
can contain are described in the section called “MYSQL
COMMANDS”.
•--protocol={TCP|SOCKET|PIPE|MEMORY}
The connection protocol to use for connecting to the server. It is useful when
the other connection parameters normally would cause a protocol to be used
other than the one you want.
•--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
For tabular output, the “boxing” around columns enables one column
value to be distinguished from another. 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. Enabled by
default, to disable use --skip-reconnect or
--disable-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
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.
This option results in nontabular output format and escaping of special
characters. Escaping may be disabled by using raw mode; see the description
for the --raw option.
•--skip-auto-rehash
Disable automatic rehashing. Synonym for --disable-auto-rehash.
•--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
Enable SSL for connection (automatically enabled with other flags). Disable with
--skip-ssl.
•--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 (check OpenSSL docs, implies --ssl).
•--ssl-cipher=name
SSL cipher to use (check OpenSSL docs, implies --ssl).
•--ssl-key=name
X509 key in PEM format (check OpenSSL docs, implies --ssl).
•--ssl-crl=name
Certificate revocation list (check OpenSSL docs, implies --ssl).
•--ssl-crlpath=name
Certificate revocation list path (check OpenSSL docs, 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.
•--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 MariaDB 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
If the connection cannot be established, wait and retry instead of
aborting.
•--xml, -X
Produce XML output. The output when --xml is used with mysql
matches that of mysqldump --xml. See mysqldump(1)
for details.
The XML output also uses an XML namespace, as shown here:
You can also set the following variables by using
--var_name =value.
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>
•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
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.
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:
You need do this only once.
shell> ln -s /dev/null $HOME/.mysql_history
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´
•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. For more information, see the section
called “MYSQL SERVER-SIDE HELP”.
•charset charset_name, \C
charset_name
Change the default character set and issue a SET NAMES statement. This enables
the character set to remain synchronized on the client and server if
mysql is run with auto-reconnect enabled (which is not recommended),
because the specified character set is used for reconnects.
•clear, \c
Clear the current input. Use this if you change your mind about executing the
statement that you are entering.
•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 MariaDB. 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, and for parsing the body of stored procedures
and functions, triggers, and events.
•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
Enable display of warnings after each statement.
•pager [command],
\P [ command]
Enable output paging. By using the --pager option when you invoke
mysql, it is possible to browse or search query results in interactive
mode with Unix programs such as less, more, or any other similar
program. If you specify no value for the option, mysql checks the value
of the PAGER environment variable and sets the pager to that. Pager
functionality works only in interactive mode.
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 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
Use db_name as the default database.
•warnings, \W
Enable display of warnings after each statement (if there are any).
Here are a few tips about the pager command:
•You can use it to write to a file and the results
go only to the file:
You can also pass any options for the program that you want to use as your
pager:
mysql> pager cat > /tmp/log.txt
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:
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.
mysql> pager cat | tee /dr1/tmp/res.txt \ | tee /dr2/tmp/res2.txt | less -n -i -S
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 |
\O | The current month in three-letter format (Jan, Feb, ...) |
\o | The current month in numeric format |
\P | am/pm |
\p | The current TCP/IP port or socket file |
\R | The current time, in 24-hour military time (0–23) |
\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 |
•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 MariaDB option file, such as /etc/my.cnf or
the .my.cnf file in your home directory. For example:
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. 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=(\\u@\\h) [\\d]>\\_
[mysql] prompt="\\r:\\m:\\s> "
•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
mysql> help me Nothing found Please try to run ´help contents´ for a list of all accessible topics
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
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 SHOW BINARY LOGS SHOW ENGINE SHOW LOGS
mysql> help show binary logs Name: ´SHOW BINARY LOGS´ Description: Syntax: SHOW BINARY LOGS SHOW MASTER LOGS 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
shell> mysql db_name < text_file
shell> mysql < text_file
mysql> source file_name mysql> \. file_name
SELECT ´<info_to_display>´ AS ´ ´;
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 MariaDB server:SET sql_safe_updates=1, sql_select_limit=1000, sql_max_join_size=1000000;
•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)
COPYRIGHT¶
Copyright 2007-2008 MySQL AB, 2008-2010 Sun Microsystems, Inc., 2010-2015 MariaDB Foundation 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
SEE ALSO¶
For more information, please refer to the MariaDB Knowledge Base, available online at https://mariadb.com/kb/AUTHOR¶
MariaDB Foundation (http://www.mariadb.org/).04/08/2015 | MariaDB 10.0 |