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How do we change the table to add a MySQL virtual generated column?

王林
Release: 2023-09-09 09:29:07
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我们如何更改表以添加 MySQL 虚拟生成列?

To add a MySQL virtual generated column to the table, we can use the same syntax as adding a column, just add "AS (expression)" after the data type, that is Can. The syntax is as follows -

Grammar

ALTER TABLE table_name
ADD COLUMN column_name AS(expression);
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Example

mysql> ALTER TABLE employee_data ADD COLUMN FULLName Varchar(200) AS(CONCAT_WS(" ", 'First_name','Last_name'));
Query OK, 0 rows affected (0.49 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> Describe employee_data;
+------------+--------------+------+-----+---------+-------------------+
| Field      | Type         | Null | Key | Default | Extra             |
+------------+--------------+------+-----+---------+-------------------+
| ID         | int(11)      | NO   | PRI | NULL    | auto_increment    |
| First_name | varchar(50)  | NO   |     | NULL    |                   |
| Last_name  | varchar(50)  | NO   |     | NULL    |                   |
| FULL_NAME  | varchar(90)  | YES  |     | NULL    | VIRTUAL GENERATED |
| FULLName   | varchar(200) | YES  |     | NULL    | VIRTUAL GENERATED |
+------------+--------------+------+-----+---------+-------------------+
5 rows in set (0.00 sec)
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source:tutorialspoint.com
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