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:

mysql> pager more
PAGER set to 'more'
mysql> select title from sakila.film;
+-----------------------------+
| title                       |
+-----------------------------+
| ACADEMY DINOSAUR            |
| ACE GOLDFINGER              |
| ADAPTATION HOLES            |
| AFFAIR PREJUDICE            |
| AFRICAN EGG                 |
| AGENT TRUMAN                |
| AIRPLANE SIERRA             |
| AIRPORT POLLOCK             |
| ALABAMA DEVIL               |
| ALADDIN CALENDAR            |
| ALAMO VIDEOTAPE             |
| ALASKA PHANTOM              |
| ALI FOREVER                 |
| ALICE FANTASIA              |
| ALIEN CENTER                |
| ALLEY EVOLUTION             |
| ALONE TRIP                  |
| ALTER VICTORY               |
| AMADEUS HOLY                |
--Plus--

mysql> pager more

PAGER set to 'more'

mysql> select title from sakila.film;

+-----------------------------+

| title |

+-----------------------------+

| ACADEMY DINOSAUR |

| ACE GOLDFINGER |

| ADAPTATION HOLES |

| AFFAIR PREJUDICE |

| AFRICAN EGG |

| AGENT TRUMAN |

| AIRPLANE SIERRA |

| AIRPORT POLLOCK |

| ALABAMA DEVIL |

| ALADDIN CALENDAR |

| ALAMO VIDEOTAPE |

| ALASKA PHANTOM |

| ALI FOREVER |

| ALICE FANTASIA |

| ALIEN CENTER |

| ALLEY EVOLUTION |

| ALONE TRIP |

| ALTER VICTORY |

| AMADEUS HOLY |

--Plus--

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:

mysql> pager grep sequence
PAGER set to 'grep sequence'
mysql> show engine innodb status\Gselect sleep(60);show engine innodb status\G
Log sequence number 380166807992
1 row in set (0.41 sec)

1 row in set (1 min 0.00 sec)

Log sequence number 380170274979
1 row in set (0.00 sec)

mysql> pager grep sequence

PAGER set to 'grep sequence'

mysql> show engine innodb status\Gselect sleep(60);show engine innodb status\G

Log sequence number 380166807992

1 row in set (0.41 sec)

1 row in set (1 min 0.00 sec)

Log sequence number 380170274979

1 row in set (0.00 sec)

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

mysql> pager
Default pager wasn't set, using stdout.

1 2	mysql> pager Default pager wasn't set, using stdout.

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:

mysql> select count(*) from film left join film_category using(film_id) left join category using(category_id) where name='Music';

1	mysql> select count(*) from film left join film_category using(film_id) left join category using(category_id) where name='Music';

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:

mysql> edit

1	mysql> 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:

mysql> tee queries.log
Logging to file 'queries.log'
mysql> use sakila
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select count(*) from sakila;
ERROR 1146 (42S02): Table 'sakila.sakila' doesn't exist
mysql> select count(*) from film;
+----------+
| count(*) |
+----------+
|     1000 |
+----------+
1 row in set (0.00 sec)

mysql> exit

mysql> tee queries.log

Logging to file 'queries.log'

mysql> use sakila

Reading table information for completion of table and column names

You can turn off this feature to get a quicker startup with -A

Database changed

mysql> select count(*) from sakila;

ERROR 1146 (42S02): Table 'sakila.sakila' doesn't exist

mysql> select count(*) from film;

+----------+

| count(*) |

+----------+

| 1000 |

+----------+

1 row in set (0.00 sec)

mysql> exit

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.

17 Comments

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Nikolay Mihaylov

11 years ago

and dont forget \G

Justin Swanhart

11 years ago

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.

Justin Swanhart

11 years ago

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.

Bill Karwin

11 years ago

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

Kolbe Kegel

11 years ago

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

Ernie Souhrada

11 years ago

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.