MySQL 如何创建一个使用表中动态数据的MySQL存储函数？

MySQL存储函数可以引用表，但不能使用返回结果集的语句。因此我们可以说，没有SELECT查询返回结果集。但我们可以有SELECT INTO来处理它。例如，我们创建一个名为“Avg_marks”的函数，它使用名为“Student_marks”的表中的动态数据，该表具有以下记录，以计算平均分数。

mysql> Select * from Student_marks;
+-------+------+---------+---------+---------+
| Name  | Math | English | Science | History |
+-------+------+---------+---------+---------+
| Raman |   95 |      89 |      85 |      81 |
| Rahul |   90 |      87 |      86 |      81 |
+-------+------+---------+---------+---------+
2 rows in set (0.00 sec)

mysql> DELIMITER //
mysql> Create Function Avg_marks(S_name Varchar(50))
    -> RETURNS INT
    -> DETERMINISTIC
    -> BEGIN
    -> DECLARE M1,M2,M3,M4,avg INT;
    -> SELECT Math,English,Science,History INTO M1,M2,M3,M4 FROM Student_marks W
HERE Name = S_name;
    -> SET avg = (M1+M2+M3+M4)/4;
    -> RETURN avg;
    -> END //
Query OK, 0 rows affected (0.01 sec)

mysql> DELIMITER ;
mysql> Select Avg_marks('Raman') AS 'Raman_Marks';
+-------------+
| Raman_Marks |
+-------------+
|          88 |
+-------------+
1 row in set (0.07 sec)

mysql> Select Avg_marks('Rahul') AS 'Raman_Marks';
+-------------+
| Raman_Marks |
+-------------+
|          86 |
+-------------+
1 row in set (0.00 sec)

阅读更多：MySQL 教程