MySQL 存储的生成列如何与数学表达式一起使用?
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2023-09-13 15:09:02
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![MySQL 存储的生成列如何与数学表达式一起使用?](//m.sbmmt.com/img/upload/article/000/000/164/169458894773892.jpg)
可以通过一个示例来说明,在该示例中,我们在名为“triangle_stored”的表中创建一个存储的生成列。我们知道,存储生成列可以通过使用关键字“stored”来生成。
mysql> Create table triangle_stored(SideA DOUBLE, SideB DOUBLE, SideC DOUBLE AS (SQRT(SideA * SideB + SideB * SideB)) STORED);
Query OK, 0 rows affected (0.47 sec)
mysql> Describe triangle_stored;
+-------+--------+------+-----+---------+------------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+------------------+
| SideA | double | YES | | NULL | |
| SideB | double | YES | | NULL | |
| SideC | double | YES | | NULL | STORED GENERATED |
+-------+--------+------+-----+---------+------------------+
3 rows in set (0.00 sec)
mysql> INSERT INTO triangle_stored(SideA, SideB) Values(1,1),(3,4),(6,8);
Query OK, 3 rows affected (0.09 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> Select * from triangle_stored;
+-------+-------+--------------------+
| SideA | SideB | SideC |
+-------+-------+--------------------+
| 1 | 1 | 1.4142135623730951 |
| 3 | 4 | 5.291502622129181 |
| 6 | 8 | 10.583005244258363 |
+-------+-------+--------------------+
3 rows in set (0.00 sec)
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