SELECT i.uid,sum(deposit+ddeposit+money) as allmoney FROM
另外,因为你是多个表的左联接,考虑到有NULL记录的存在,建议你用函数ifnull处理下,避免由于NULL而造成结果有误,最终改成这样:
SELECT i.uid,sum(ifnull(deposit,0)+ifnull(ddeposit,0)+ifnull(money,0)) as allmoney
FROM pw_memberinfo i LEFT JOIN pw_members m ON m.uid=i.uid LEFT JOIN pw_memberdata d ON i.uid=d.uid
where ifnull(deposit,0)+ifnull(ddeposit,0)+ifnull(money,0)>2000;