我在MySQL中有两个表,如下所示:ID (Primary Key Auto Increment) | Student Name | AgeTeacher Name| Student ID (This is the Student ID from table1) | Email | Education学生姓名|年龄|教师姓名
请
我在MySQL表中有两列,一个是startDay varchar(10),比如"2020-03-23",另一个是orderId archer(20),它们都可以为空 select * from table where orderId is null and startDay < '2020-03-23'
select * from tablewhere orderId is not null and startDay <