[英]SQL trigger, check if certain value was entered
INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
Now what to check: 现在检查一下:
If inserted value1 = null, change it to 0 如果插入value1 = null,则将其更改为0
How to do it via trigger? 如何通过触发器来做到这一点? I googled for examples and I have never ever done a trigger, so it is rather confusing.
我用谷歌搜索了一些例子,我从来没有做过触发器,所以它相当令人困惑。
So far got only this: 到目前为止只有这个:
CREATE TRIGGER testTrigger
ON myTable
AFTER INSERT, UPDATE, DELETE
You can add default value . 您可以添加默认值 。 This is how it's done for a new column.
这就是新列的完成方式。 For existing one you should add constraint.
对于现有的,您应该添加约束。 Check Update 2
检查更新2
ALTER TABLE table_name
ADD column1 int NOT NULL DEFAULT(0)
Add a column with a default value to an existing table in SQL Server 将具有默认值的列添加到SQL Server中的现有表
UPDATE: 更新:
To set default value, you should update NULL values at first. 要设置默认值,首先应更新NULL值。
UPDATE table_name
SET column1 = 0
WHERE column1 IS NULL
UPDATE 2: 更新2:
Try adding constraint 尝试添加约束
ALTER TABLE table_name
ADD CONSTRAINT DF_column1 DEFAULT 0 FOR column1
You could write this in the trigger: 你可以在触发器中写这个:
UPDATE T SET value1 =0
FROM table_name T
JOIN INSERTED I
ON T.<id>=I.<id>
WHERE I.value1 is null
INSERTED table which is accessible only within trigger will store the values that have inserted.. 只能在触发器中访问的INSERTED表将存储已插入的值。
在INSERTED值上使用ISNULL
SELECT ISNULL(INSERTED,0) FROM INSERTED
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