java sql 创建触发器_JavaEE进阶 SQL Server 触发器
SQL Server 触发器
触发器是一种特殊类型的存储过程，它不同于之前的我们介绍的存储过程。触发器主要是通过事件进行触发被自动调用执行的。而存储过程可以通过存储过程的名称被调用。本篇JavaEE进阶教程将为大家讲解JavaEE进阶编程的知识点，看完这篇文章会让你对JavaEE进阶编程的知识点有更加清晰的理解和运用。
DML触发器分为：
1、 after触发器(之后触发)
a、 insert触发器
b、 update触发器
c、 delete触发器
2、 instead of 触发器 (之前触发)
触发器有两个特殊的表：插入表(instered表)和删除表(deleted表)。这两张是逻辑表也是虚表。由系统在内存中创建者两张表，不会存储在数据库中。而且两张表的都是只读的，只能读取数据而不能修改数据。这两张表的结果总是与被改触发器应用的表的结构相同。当触发器完成工作后，这两张表就会被删除。Inserted表的数据是插入或是修改后的数据，而deleted表的数据是更新前的或是删除的数据。
创建触发器
语法
创建触发器
语法create trigger tgr_name
on table_name
with encrypion –加密触发器
for update…
as
Transact-SQL
# 创建insert类型触发器
–创建insert插入类型触发器if (object_id(‘tgr_classes_insert’, ‘tr’) is not null)
drop trigger tgr_classes_insert
go
create trigger tgr_classes_insert
on classes
for insert –插入触发
as
–定义变量declare @id int, @name varchar(20), @temp int;
–在inserted表中查询已经插入记录信息
select @id = id, @name = name from inserted;
set @name = @name + convert(varchar, @id);
set @temp = @id / 2;
insert into student values(@name, 18 + @id, @temp, @id);
print ‘添加学生成功！’;
go
–插入数据insert into classes values(‘5班’, getDate());
–查询数据select * from classes;
select * from student order by id;
insert触发器，会在inserted表中添加一条刚插入的记录。
# 创建delete类型触发器
–delete删除类型触发器if (object_id(‘tgr_classes_delete’, ‘TR’) is not null)
drop trigger tgr_classes_delete
go
create trigger tgr_classes_delete
on classes
for delete –删除触发
as
print ‘备份数据中……’;
if (object_id(‘classesBackup’, ‘U’) is not null)
–存在classesBackup，直接插入数据
insert into classesBackup select name, createDate from deleted;
else
–不存在classesBackup创建再插入
select * into classesBackup from deleted;
print ‘备份数据成功！’;
go
–不显示影响行数–set nocount on;
delete classes where name = ‘5班’;
–查询数据select * from classes;
select * from classesBackup;
delete触发器会在删除数据的时候，将刚才删除的数据保存在deleted表中。
# 创建update类型触发器
–update更新类型触发器if (object_id(‘tgr_classes_update’, ‘TR’) is not null)
drop trigger tgr_classes_update
go
create trigger tgr_classes_update
on classes
for update
as
declare @oldName varchar(20), @newName varchar(20);
–更新前的数据select @oldName = name from deleted;
if (exists (select * from student where name like ‘%’+ @oldName + ‘%’))
begin
–更新后的数据select @newName = name from inserted;
update student set name = replace(name, @oldName, @newName) where name like ‘%’+ @oldName + ‘%’;
print ‘级联修改数据成功！’;
end
else
print ‘无需修改student表！’;
go
–查询数据select * from student order by id;
select * from classes;
update classes set name = ‘五班’ where name = ‘5班’;
update触发器会在更新数据后，将更新前的数据保存在deleted表中，更新后的数据保存在inserted表中。
# update更新列级触发器if (object_id(‘tgr_classes_update_column’, ‘TR’) is not null)
drop trigger tgr_classes_update_column
go
create trigger tgr_classes_update_column
on classes
for update
as
–列级触发器：是否更新了班级创建时间if (update(createDate))
begin
raisError(‘系统提示：班级创建时间不能修改！’, 16, 11);
rollback tran;
end
go
–测试select * from student order by id;
select * from classes;
update classes set createDate = getDate() where id = 3;
update classes set name = ‘四班’ where id = 7;
更新列级触发器可以用update是否判断更新列记录；
# instead of类型触发器
instead of触发器表示并不执行其定义的操作(insert、update、delete)而仅是执行触发器本身的内容。
创建语法create trigger tgr_name
on table_name
with encryption
instead of update…
as
T-SQL
# 创建instead of触发器if (object_id(‘tgr_classes_inteadOf’, ‘TR’) is not null)
drop trigger tgr_classes_inteadOf
go
create trigger tgr_classes_inteadOf
on classes
instead of delete/*, update, insert*/
as
declare @id int, @name varchar(20);
–查询被删除的信息，并赋值select @id = id, @name = name from deleted;
print ‘id: ’ + convert(varchar, @id) + ‘, name: ’ + @name;
–先删除student的信息delete student where cid = @id;
–再删除classes的信息delete classes where id = @id;
print ‘删除[ id: ’ + convert(varchar, @id) + ‘, name: ’ + @name + ’ ] 的信息成功！’;
go
–test
select * from student order by id;
select * from classes;
delete classes where id = 7;
# 显示自定义消息raiserrorif (object_id(‘tgr_message’, ‘TR’) is not null)
drop trigger tgr_message
go
create trigger tgr_message
on student
after insert, update
as raisError(‘tgr_message触发器被触发’, 16, 10);
go
–test
insert into student values(‘lily’, 22, 1, 7);
update student set sex = 0 where name = ‘lucy’;
select * from student order by id;
# 修改触发器alter trigger tgr_message
on student
after delete
as raisError(‘tgr_message触发器被触发’, 16, 10);
go
–test
delete from student where name = ‘lucy’;
# 启用、禁用触发器
–禁用触发器disable trigger tgr_message on student;
–启用触发器enable trigger tgr_message on student;
# 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 t
on t.object_id = te.object_id
where 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_data
go
create trigger tgr_valid_data
on student
after insert
as
declare @age int,
@name varchar(20);
select @name = s.name, @age = s.age from inserted s;
if (@age
begin
raisError(‘插入新数据的age有问题’, 16, 1);
rollback tran;
end
go
–test
insert 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 log
go
create table log(
id int identity(1, 1) primary key,
action varchar(20),
createDate datetime default getDate()
)
go
if (exists (select * from sys.objects where name = ‘tgr_student_log’))
drop trigger tgr_student_log
go
create trigger tgr_student_log
on student
after insert, update, delete
as
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’);
end
go
–test
insert 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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