(1) SQL databases may not be able to accept special characters (like $, @, &) as valid inputs.
(2) Data sent to the database server may be corrupted due to packet losses caused by slow connections.
(3) Proper implementation of database rollback logic. Otherwise, it causes data corruption. Design your test cases to exercise those critical areas.
(4) Check for complete loading of tables in the database.
(5) Check for proper error handling.
(6) Check that your server does not run out of disk space.