如何在MySQL GROUP BY子句中排序或选择行？
让我们首先创建一个表-
mysql> create table DemoTable1572 -> ( -> StudentId int, -> StudentMarks int, -> StudentName varchar(20) -> );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1572 values(1,79,'Sam'); mysql> insert into DemoTable1572 values(2,89,'Chris'); mysql> insert into DemoTable1572 values(3,98,'David'); mysql> insert into DemoTable1572 values(4,79,'Bob');
使用select语句显示表中的所有记录-
mysql> select * from DemoTable1572;
这将产生以下输出-
+-----------+--------------+-------------+ | StudentId | StudentMarks | StudentName | +-----------+--------------+-------------+ | 1 | 79 | Sam | | 2 | 89 | Chris | | 3 | 98 | David | | 4 | 79 | Bob | +-----------+--------------+-------------+ 4 rows in set (0.00 sec)
这是对MySQLGROUPBY子句中的行进行排序或选择的查询-
mysql> select * from DemoTable1572 -> where StudentId in (select min(StudentId) from DemoTable1572 group by StudentMarks);
这将产生以下输出-
+-----------+--------------+-------------+ | StudentId | StudentMarks | StudentName | +-----------+--------------+-------------+ | 1 | 79 | Sam | | 2 | 89 | Chris | | 3 | 98 | David | +-----------+--------------+-------------+ 3 rows in set (0.10 sec)