在MySQL中按顺序调用聚合函数

为此，使用GROUP_CONCAT()和ORDER BY子句。让我们先创建一个表 –

mysql> create table DemoTable1588
  -> (
  -> StudentId int,
  -> StudentFirstName varchar(20),
  -> StudentMarks int
  -> );
Query OK, 0 rows affected (0.49 sec)

使用insert命令在表中插入一些记录 –

mysql> insert into DemoTable1588 values(110,'Bob',78);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable1588 values(101,'Sam',78);
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable1588 values(105,'Mike',78);
Query OK, 1 row affected (0.26 sec)

使用select语句显示表中的所有记录 –

mysql> select * from DemoTable1588;

这将产生以下输出 –

+-----------+------------------+--------------+
| StudentId | StudentFirstName | StudentMarks |
+-----------+------------------+--------------+
|       110 | Bob              |           78 |
|       101 | Sam              |           78 |
|       105 | Mike             |           78 |
+-----------+------------------+--------------+
3 rows in set (0.00 sec)

这是一个按顺序调用聚合函数的查询 –

mysql> select group_concat(StudentFirstName order by StudentId separator '--') from DemoTable1588
  -> group by StudentMarks;

这将产生以下输出 –

+------------------------------------------------------------------+
| group_concat(StudentFirstName order by StudentId separator '--') |
+------------------------------------------------------------------+
| Sam--Mike--Bob                                                   |
+------------------------------------------------------------------+
1 row in set (0.04 sec)

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