July 14, 2014

Be productive with the MySQL command line

Even if you are using a GUI tool to connect to your MySQL servers, one day or another, you will have to deal with the command line. So it is nice to know a few tips that can really make your work easier.

Note: The commands below are only available for Unix/Linux.

Using pager

Most of the graphical tools paginate results, which is very handy. But this is not the way the command line client works: it just outputs all results. It can be annoying but it is easily solved by using the pager command:

Another example of the pager command is when you want to estimate a good size for you InnoDB redo logs: the estimation is based on the variation of the Log Sequence Number during a given period of time. Instead of manually looking for the right line in the output of SHOW ENGINE INNODB STATUS (which can be huge), you can call pager to the rescue:

When you are done and you want to disable paging, you can simply run:

Using edit

When you try to optimize a query, it often involves manipulating the text of the query, and sometimes it would be great to have a text editor inside the client. Well, this can be achieved by using the edit command.

Let’s say you have the following query:

and let’s say you want to change the left joins to inner joins and use capital letters for reserved SQL words. Instead of manually editing the statement, which will be boring, you simply call edit:

and it will open your default text editor with the text of the last query. The default text editor is vi, so you now have the power of vi inside the mysql client!
Once you have made your changes, save and exit the editor: you are back in the mysql client where you can type ; or \G to execute the query.

Using tee

In some situations, like when you are testing a set of commands to write documentation or when you are in the middle of an emergency, you want to be able to record the queries that you have executed. The command line client offers the tee command, which will log to a file the statements you typed and their output, pretty much like the Unix tee command:

And now if you look at the content of the queries.log file, you will see a copy of your session.

Conclusion

The mysql command line client is not as glossy as most of the graphical tools, but if you know some of its hidden features, it can be very powerful. If you enjoyed these tips, I will write another post with other useful but overlooked features.

About Stephane Combaudon

Stéphane joined Percona in July 2012, after working as a MySQL DBA for leading French companies such as Dailymotion and France Telecom.

In real life, he lives in Paris with his wife and their twin daughters. When not in front of a computer or not spending time with his family, he likes playing chess and hiking.

Comments

  1. and dont forget \G

  2. Justin Swanhart says:

    Also you can use readline shortcuts in Linux (won’t work in Windows):
    CTRL-r (search backward in history)
    CTRL-a (go to end of line)
    CTRL-e (go to start of line)
    CTRL-w (delete word before cursor)
    META-f (go forward one word)
    etc..

    \? shows help

    \n or \P alone will turn off the pager depending on your client

    source (\.) will execute an SQL file

    prompt – you can change the prompt. this is useful in you .my.cnf. You can make root’s prompt read with ANSI escape sequences for example.

  3. Justin Swanhart says:

    That should have read:
    prompt – you can change the prompt. this is useful in your .my.cnf. You can make root’s prompt RED with ANSI escape sequences for example.

  4. I sometimes set my pager to pt-visual-explain.

  5. Kolbe Kegel says:

    Justin,

    Sadly, the readline shortcuts don’t quite work with the MySQL 5.6 client. Oracle appears to have chosen to start using “EditLine” instead of “readline” for their builds and the semantics for searching/scrolling/skipping through your command-line and command-line history are considerably different than in previous releases. I’ve found it to be very confusing to try to edit commands in 5.6 compared to a decade of earlier releases of MySQL. (Anyone who’s been using commercially-licensed “mysql” will feel right at home; EditLine has been used for many years in commercially-licensed builds of the MySQL Client.)

    Kolbe

  6. Ernie Souhrada says:

    One of my personal favorites is “pager md5sum” .. I use it as a nice quick way to compare whether or not two queries (of any kind) are returning the same results.

  7. Yin Xi says:

    I like tee, very useful

  8. Geoffrey Lee says:

    Great tips for the MySQL CLI. Please do post more!

  9. yuanbin says:

    very good,tks!

  10. The pager feature is nice, but not available on all platforms (windows).

    It’s possible to used md5sum/sha1sum as a pager to check if the output for two queries is the same. This could be handy after rewriting a query.

  11. Cédric says:

    This one is nice too : http://mysql.wisborg.dk/2012/12/25/merry-christmas/
    Happy 2013.
    Bye

  12. marc says:

    Alittle late to this post, but I don’t know how I ever lived without knowing about ‘edit’. Great tip!

  13. kan says:

    useful

  14. Awesome.. i was facing hard time with pagination. I did knot knew about pager command. Thanks for sharing.

  15. John says:

    Hi Stephane,

    I never knew about pager before now, thanks.

    If you are looking for a command line tool for graphing (perhaps query performance charts) I recommend sqlchart (http://sqldashboards.com/sqlchart)

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