Question

php查询表字段是否为空怎么写语句？

根据uid查询某个会员的密码是否为空
表 member 字段 password uid=888
完整的查询语句怎么写？

Answer 1

空有2种，一种是null，一种是什么都没有，
个人认为，这两种情况都需要判断
select * from `member` whre `uid` = 888 and `password` is null and `password` = ''

Answer 2

sql="select * from member where password=null and uid='888'";

Answer 3

SELECT * from `member` WHERE uid=888 AND password IS NULL