I don't like MySQL for various resons, most important one being that I saw PostgreSQL early on and never looked back.

Here are few quick commands to ease my pain:

Number of rows in table

select count(*) from table_name is terrably slow in MySQL, so use information schema to quickly have report...

mysql> select table_name,table_rows,avg_row_length,data_length
 from information_schema.tables
 where table_type = 'BASE TABLE'
 order by table_rows desc
 limit 10 ;
+-----------------+------------+----------------+-------------+
| table_name      | table_rows | avg_row_length | data_length |
+-----------------+------------+----------------+-------------+
| zebraqueue      |    2309022 |             87 |   200998912 | 
| sessions        |    1744788 |            675 |  1178402816 | 
| items           |     302540 |            126 |    38338560 | 
| biblio          |     268391 |            166 |    44646400 | 
| action_logs     |     225797 |            341 |    77168640 | 
| biblioitems     |     220004 |           8159 |  1795080192 | 
| items_print_log |     205559 |            104 |    21528576 | 
| statistics      |     130166 |             76 |     9977856 | 
| old_issues      |      43852 |             84 |     3686400 | 
| import_biblios  |      19352 |            136 |     2637824 | 
+-----------------+------------+----------------+-------------+
10 rows in set (1.90 sec)

Create grepable dump

Put every value in it's own line

mysqldump -u user -p database --extended-insert=0 > dump.sql

Poor man's graphs

mysql> select dateenrolled,count(*),rpad('',count(*) / 10,'*') from borrowers group by dateenrolled;
+--------------+----------+----------------------------------------------+
| dateenrolled | count(*) | rpad('',count(*) / 10,'*')                   |
+--------------+----------+----------------------------------------------+
| NULL         |       18 | **                                           | 
| 2008-04-03   |        1 |                                              | 
| 2008-04-17   |        1 |                                              | 
| 2008-05-28   |        1 |                                              | 
| 2008-06-05   |        1 |                                              | 
| 2008-06-12   |        3 |                                              | 
| 2008-07-28   |        1 |                                              | 
| 2008-10-17   |        1 |                                              | 
| 2008-10-20   |        1 |                                              | 
| 2008-10-21   |        1 |                                              | 
| 2008-10-27   |       11 | *                                            | 
| 2008-10-28   |        2 |                                              | 
| 2008-10-29   |        4 |                                              | 
| 2008-10-30   |        2 |                                              | 
| 2008-11-03   |        1 |                                              | 
| 2008-11-04   |        9 | *                                            | 
| 2008-11-06   |        7 | *                                            | 
| 2008-11-10   |       16 | **                                           | 
| 2008-11-11   |        1 |                                              | 
| 2008-11-13   |        1 |                                              | 
| 2008-11-14   |        4 |                                              | 
| 2008-11-17   |        1 |                                              | 
| 2008-11-20   |        1 |                                              | 
| 2008-11-26   |        1 |                                              | 
| 2008-12-02   |        1 |                                              | 
| 2008-12-19   |        2 |                                              | 
| 2009-01-07   |        2 |                                              | 
| 2009-03-16   |      301 | ******************************               | 
| 2009-03-17   |      365 | *************************************        | 
| 2009-03-18   |      439 | ******************************************** | 
| 2009-03-19   |      324 | ********************************             | 
| 2009-03-20   |      226 | ***********************                      | 
| 2009-03-23   |      105 | ***********                                  | 
+--------------+----------+----------------------------------------------+
33 rows in set (0.00 sec)

MySQL Koha utf-8 encoding

connect

use DBI();

my $dbh = DBI->connect ('dbi:mysql:test_db', $username, $password, 
   {mysql_enable_utf8 => 1}
);

my.cnf performance optimization

• https://launchpad.net/mysql-tuning-primer
• https://launchpad.net/mysqltuner/
• http://github.com/rackerhacker/MySQLTuner-perl

Performance monitoring

./mk-query-digest --processlist localhost --interval 0.01

Linux tuning

# turn off readahead
hdparm -a 0 /dev/sdb

# noop/deadline better than cfq
echo noop > /sys/block/sdb/queue/scheduler