Error:

SELECT HistoryId, IMEINo, HistoryDtTm, Description, Credits, CreditsLeft, FeePercentage FROM tbl_gf_credit_history WHERE UserId = ORDER BY HistoryId DESC limit 0, 50

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ORDER BY HistoryId DESC limit 0, 50' at line 2