mysql 查询出某字段的值不为空的语句
1.不为空
select * from table where id <> "";
select * from table where id != "";
select * from table where is not null;
2.为空
select * from table where id ="";
select * from table where isNull(id);
select * from table where id is null;
一个对数据库感兴趣的小白