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How do MySQL stored generated columns work with mathematical expressions?

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2023-09-13 15:09:02557browse

MySQL 存储的生成列如何与数学表达式一起使用?

This can be illustrated with an example where we create a stored generated column in a table named "triangle_stored". We know that stored generated columns can be generated by using the keyword "stored".

Example

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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