(This is part 9 in a series, part 8 is here – because reverse chronological order totally makes sense here)

So, back around 2007, somebody noticed that an awful lot of the downloads of MySQL and associated utilities from mysql.com were for Windows. Of course, it’s then immediately pointed out that the vast majority of Linux users will not be heading to mysql.com to download MySQL, instead using the packages from their distribution.

However, the number of people working on MySQL who had ever even attempted to compile the MySQL server on Windows when given the number of mysql users on Windows was… well…. rather embarrassing. This is very common with free and open source software – especially historically.

If you look back 10 years, Linux on the …

Any person with half a brain would see from the error messages below that the MySQL server is not operating optimally, or more specifically the MySQL upgrade has not completely successfully and let users can go happily use the website. It amazing me when web hosting providers tell their paying client that an upgrade has been performed yet they did not have the intelligence to actually look at the error log for confirmation. Got a mysql> prompt, it’s all good. One of the first things I check is the error log.

When will people learn the MySQL error log is a valuable resource both for what it contains, and what it should not contain.

120426 17:36:00 [Note] /usr/libexec/mysqld: Shutdown complete

120426 17:36:00 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
120426 17:36:00 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
120426 17:36:00 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: …

What is going on with the version numbers coming out of Sun/MySQL?Once upon a time, we had 5.2.Then, to incorporate Falcon, it became 6.0.Somewhere along the line, there was a 5.3.Then a 5.4 appeared which seemed to be 5.1 with performance fixes for InnoDB.Now there is a 5.5, which claims to be a 5.4 with a few stuff added.Stop confusing your community.And whatever happened to community

The Daily WTF collects excellent tales from the real world. These days, the dismal dramatic sagas are often (at least in part) about mistakes involving databases; no surprise there, they’re so prolific…

Anyway, if you can learn from other people’s mistakes, that’s cheap and efficient education! I thought I’d share today’s edition with you: it’s called Death by Delete. Read and enjoy^H^H^H^H^Hlearn.

Well… kinda… (and nobody make fun of me for using my MythTV box as a testing ground for SQL against MySQL).

myth@orpheus:~$ mysql -u root test
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2496
Server version: 5.0.51a-3ubuntu5.4-log (Ubuntu)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> create table t1 (a tinytext default 'fail');
ERROR 1101 (42000): BLOB/TEXT column 'a' can't have a default value
mysql> create table t1 (a tinytext default '');
Query OK, 0 rows affected, 1 warning (0.07 sec)

mysql> show warnings;
+---------+------+-------------------------------------------------+
| Level   | Code | Message                                         |
+---------+------+-------------------------------------------------+
| Warning | 1101 | BLOB/TEXT column 'a' can't have a default value |
+---------+------+-------------------------------------------------+
1 row in set (0.00 sec)

As documented, the FLOAT datatype does not guarantee precise storage of decimal values. But where the non-precision is apparent can be a little confusing - take the following example:

mysql> CREATE TABLE my_table (a FLOAT);
Query OK, 0 rows affected (0.25 sec)

mysql> insert into my_table (a) VALUES ('2.2');
Query OK, 1 row affected (0.08 sec)

mysql> SELECT * FROM my_table WHERE a = 2.2;
Empty set (0.05 sec)

mysql> SELECT a, IFNULL(a,0) FROM my_table;
+------+-----------------+
| a    | IFNULL(a,0)     |
+------+-----------------+
|  2.2 | 2.2000000476837 | 
+------+-----------------+
1 row in set (0.00 sec)

mysql> SELECT a, a+0 FROM my_table;
+------+-----------------+
| a    | a+0             |
+------+-----------------+
|  2.2 | 2.2000000476837 | 
+------+-----------------+
1 row in set (0.00 sec)

Need precision? Try Decimal.