黑马程序员-触发器

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数据库表：



创建语句：

--table1

CREATE TABLE [dbo].[table1](

[id] [int] IDENTITY(1,1) NOT NULL,

[value] [varchar](10) NULL,

CONSTRAINT [PK_table] PRIMARY KEY CLUSTERED

(

[id] ASC

)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

) ON [PRIMARY]

--table2

CREATE TABLE [dbo].[table2](

[id] [int] IDENTITY(1,1) NOT NULL,

[count] [int] NOT NULL,

CONSTRAINT [PK_table2] PRIMARY KEY CLUSTERED

(

[id] ASC

)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

) ON [PRIMARY]

insert into table2(count) values(0)

--触发器语句，对table1进行插入或者删除操作会触发触发器更新table1的行数

CREATE TRIGGER insert_table1 ON table1

FOR INSERT , DELETE

AS BEGIN

UPDATE table2 set count=(SELECT count(*) FROM table1) WHERE id=1;

END;

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触发器知识：

一般格式：

CREATE TRIGGER <触发器名>

{BEFORE | AFTER} <触发事件> ON <表名>

FOR EACH {ROW | STATEMENT}

[WHEN <触发条件>]

<触发动作体>

触发事件：可以是INSERT、DELETE或UODATE，也可以是几个事件的组合。

触发器类型：可以分为行级触发器（FOR EACH ROW）和语句级触发器（FOR EACH STATEMENT）



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ASP.Net+Unity开发、.Net培训、期待与您交流！ ----------------------详细请查看：www.itheima.com