Question

我的案例更新存在问题

我有一张名为diccionary的表

+-----------------------------------------------------------------------+
| id   |  table_name   |  col_name |  size    |   precis   | data_type  |
+------+---------------+-----------+----------+------------+------------+
|  1   |  'user'       |  'id'     |  null    |   10       |  'int'     |
|  2   |  'user'       | 'name'    |  255     |   null     |  'varchar' | 
|  3   |  'user'       |'lastname' |  255     |   null     |  'varchar' |
|  4   |  'user'       | 'age'     |  null    |     2      |  'varchar' |

我尝试使用此查询

UPDATE diccionary SET
size = CASE WHEN id = 2 THEN 250 END,
data_type = CASE when id = 4 THEN 'int' END;

但我收到此错误

#1048 - Column 'data_type' cannot be null

我的查询有什么问题？感谢

Answer 1

data_type列不能为空，所以你只需管理不等于4的情况，例如：assign varchar

UPDATE diccionary 
SET size = CASE WHEN id = 2 THEN 250 END,
data_type = CASE when id = 4 THEN 'int' ELSE 'varchar' END;

Answer 2

好吧，如果列不为null，则需要一个默认值。尝试添加＆＃39; ELSE＆＃39;条件：

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MySql更新案例不能为空

2 个答案: