While running some mysql scripts I suddenly hit the following error:
[cce_bash]
ERROR 1305 (42000) at line 1: FUNCTION somedatabase.find_in_set does not exist
[/cce_bash]
Since find_in_set is a standard function I was kind of puzzled, especially since I ran the same script before on some other servers without error.  Checking the SQL script I found the issue:

I had
[cce_sql]
update [blah blah] where find_in_set (id,(select [more blah[)) from [rest of blag];
[/cce_sql]
and it has to be
[cce_sql]
update [blah blah] where find_in_set(id,(select [more blah[)) from [rest of blag];
[/cce_sql]
Notice the space between the function and the opening parenthesis. At least this was the issue on the mysql version shipping with the latest CentOS 5.x; the same query worked on a CentOS 6.x mysql returning only a warning.