针对“sqlserver中触发器+游标操作实现”的完整攻略,我们可以分为以下几个步骤:
1.创建触发器,指定触发事件
在SQL Server中,要创建触发器可以使用CREATE TRIGGER语句。在语句中指定触发事件:INSERT、UPDATE或DELETE。示例代码如下:
CREATE TRIGGER example_trigger
ON example_table
AFTER INSERT, UPDATE, DELETE
AS
BEGIN
-- 在此处添加你的代码
END
2.编写游标,根据需要遍历数据
游标是SQL Server中用于遍历数据的一种方式,可以使用DECLARE CURSOR语句声明和定义游标。在游标里面,可以编写自己的SQL查询语句,并通过FETCH NEXT语句来逐条遍历数据。示例代码如下:
DECLARE example_cursor CURSOR FOR
SELECT column1, column2, column3
FROM example_table
WHERE column4 = 'example_value'
DECLARE @column1 int, @column2 varchar(50), @column3 datetime
OPEN example_cursor
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
WHILE @@FETCH_STATUS = 0
BEGIN
-- 在此处添加你的代码
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
END
CLOSE example_cursor
DEALLOCATE example_cursor
3.在触发器中调用游标
要在触发器中调用游标,只需要将游标的代码放到触发器的BEGIN和END之间即可。在调用游标之前,可以使用内置的表Inserted或Deleted来访问触发事件中的数据。示例代码如下:
CREATE TRIGGER example_trigger
ON example_table
AFTER INSERT, UPDATE, DELETE
AS
BEGIN
DECLARE example_cursor CURSOR FOR
SELECT column1, column2, column3
FROM example_table
WHERE column4 = 'example_value'
DECLARE @column1 int, @column2 varchar(50), @column3 datetime
OPEN example_cursor
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
WHILE @@FETCH_STATUS = 0
BEGIN
-- 在此处添加你的代码
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
END
CLOSE example_cursor
DEALLOCATE example_cursor
END
4.示例说明
下面给出两个示例说明,包括触发器和游标的创建、数据遍历和修改等操作。
示例一:在触发器中遍历全部数据,并将所有整数列值乘以2更新回数据库中。
创建表:
CREATE TABLE example_table
(
column1 int,
column2 varchar(50),
column3 datetime,
column4 varchar(50)
)
创建触发器:
CREATE TRIGGER example_trigger
ON example_table
AFTER INSERT, UPDATE, DELETE
AS
BEGIN
DECLARE example_cursor CURSOR FOR
SELECT column1, column2, column3
FROM example_table
DECLARE @column1 int, @column2 varchar(50), @column3 datetime
OPEN example_cursor
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
WHILE @@FETCH_STATUS = 0
BEGIN
IF @column1 IS NOT NULL
BEGIN
UPDATE example_table SET column1 = @column1 * 2 WHERE CURRENT OF example_cursor
END
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
END
CLOSE example_cursor
DEALLOCATE example_cursor
END
示例二:在触发器中只遍历新增数据,并将新加入数据的整数列值乘以2更新回数据库中。
创建表:
CREATE TABLE example_table
(
column1 int,
column2 varchar(50),
column3 datetime,
column4 varchar(50)
)
创建触发器:
CREATE TRIGGER example_trigger
ON example_table
AFTER INSERT
AS
BEGIN
DECLARE example_cursor CURSOR FOR
SELECT column1, column2, column3
FROM inserted
DECLARE @column1 int, @column2 varchar(50), @column3 datetime
OPEN example_cursor
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
WHILE @@FETCH_STATUS = 0
BEGIN
IF @column1 IS NOT NULL
BEGIN
UPDATE example_table SET column1 = @column1 * 2 WHERE column1 = @column1
END
FETCH NEXT FROM example_cursor INTO @column1, @column2, @column3
END
CLOSE example_cursor
DEALLOCATE example_cursor
END
以上是完整攻略。
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