选择查询以显示具有最大日期的重复值
为此，请使用GROUPBY和HAVING。让我们首先创建一个表-
mysql> create table DemoTable ( StudentName varchar(100), DueDate date );
示例
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values('John','2019-01-11');
mysql> insert into DemoTable values('Chris','2019-02-11');
mysql> insert into DemoTable values('Chris','2019-03-11');
mysql> insert into DemoTable values('John','2019-04-11');
mysql> insert into DemoTable values('Bob','2019-05-11');
mysql> insert into DemoTable values('Bob','2019-06-11');
mysql> insert into DemoTable values('Robert','2019-07-11');
mysql> insert into DemoTable values('Robert','2019-08-11');
mysql> insert into DemoTable values('Robert','2019-09-11');使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
输出结果
+-------------+------------+ | StudentName | DueDate | +-------------+------------+ | John | 2019-01-11 | | Chris | 2019-02-11 | | Chris | 2019-03-11 | | John | 2019-04-11 | | Bob | 2019-05-11 | | Bob | 2019-06-11 | | Robert | 2019-07-11 | | Robert | 2019-08-11 | | Robert | 2019-09-11 | +-------------+------------+ 9 rows in set (0.00 sec)
以下是查询以显示具有最大日期的重复值-
mysql> select tbl.StudentName,max(tbl.DueDate) from DemoTable tbl group by tbl.StudentName having count(*) > 1;
输出结果
+-------------+------------------+ | StudentName | max(tbl.DueDate) | +-------------+------------------+ | John | 2019-04-11 | | Chris | 2019-03-11 | | Bob | 2019-06-11 | | Robert | 2019-09-11 | +-------------+------------------+ 4 rows in set (0.00 sec)