This came in very handy for me at one point because I needed to have a certain field in each row 14 characters long, but half of them were only 12 characters long.

In MySQL:
[code lang=”sql”]
update `table` set `field` = CONCAT(`field`, ‘1’) where LEN(`field`) = 13;
[/code]

In MSSQL:
[code lang=”sql”]
update `table` set `field` = CONCAT(`field`, ‘1’) where LENGTH(`field`) = 13;
[/code]