SQL Server 触发器实例详解(2)

# 查询创建的触发器信息

--查询已存在的触发器select * from sys.triggers;select * from sys.objects where type = 'TR';--查看触发器触发事件select te.* from sys.trigger_events te join sys.triggers ton t.object_id = te.object_idwhere t.parent_class = 0 and t.name = 'tgr_valid_data';--查看创建触发器语句exec sp_helptext 'tgr_message'; 

# 示例，验证插入数据

if ((object_id('tgr_valid_data', 'TR') is not null)) drop trigger tgr_valid_datagocreate trigger tgr_valid_dataon studentafter insertas declare @age int, @name varchar(20); select @name = s.name, @age = s.age from inserted s; if (@age < 18) begin raisError('插入新数据的age有问题', 16, 1); rollback tran; endgo--testinsert into student values('forest', 2, 0, 7);insert into student values('forest', 22, 0, 7);select * from student order by id;

# 示例，操作日志

if (object_id('log', 'U') is not null) drop table loggocreate table log( id int identity(1, 1) primary key, action varchar(20), createDate datetime default getDate())goif (exists (select * from sys.objects where name = 'tgr_student_log')) drop trigger tgr_student_loggocreate trigger tgr_student_logon studentafter insert, update, deleteas if ((exists (select 1 from inserted)) and (exists (select 1 from deleted))) begin insert into log(action) values('updated'); end else if (exists (select 1 from inserted) and not exists (select 1 from deleted)) begin insert into log(action) values('inserted'); end else if (not exists (select 1 from inserted) and exists (select 1 from deleted)) begin insert into log(action) values('deleted'); endgo--testinsert into student values('king', 22, 1, 7);update student set sex = 0 where name = 'king';delete student where name = 'king';select * from log;select * from student order by id;

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