我是一个初学者，SQL怎么写事务？请高手帮帮忙！！！！

事务控制语句 (transaction)

事务就是一系列的 *** 作,要么同时完成,要么不完成

都是由一个dml语句开始的

updata emp2 set sal=sal*2

delete from dept2

insert into salgrade values (6,10000,20000)

//这样是一个transaction语句,如果使用rollback返回,则上面三条语句将不起任何作用

transaction语句的结束为 1.rollback transaction语句结束.

2.commit提交完成,transaction语句结束

3.执行ddl,或则dcl语句事务自动提交.

4.当用户正常断开连接时,transcation自动提交

5.当用户非正常断开连接时,Oracle自动执行rollback语句

如:select * from dept2//transcation开始

create table t (a varchar2(20))//执行了ddl语句,则transcation语句自动提交

sqlserver:

begin try

begin tran

update 1

update 2

end tran

commit tran

end try

begin catch

rollback tran

end catch

以oracle自带的scott为例：

1、select

t1.ename,t2.ename

as

mgrname,d.dname

from

scott.emp

t1,scott.emp

t2,scott.dept

d

where

t1.mgr=t2.empno

and

t2.deptno=d.deptno

2、select

d.*

from

scott.dept

d,(select

rownum

n,

tt.*

from

(select

count(*)

c,deptno

from

scott.emp

group

by

deptno

order

by

c

desc)

tt)t

where

t.n=1

and

t.deptno=d.deptno

3、select

*

from(select

t.*,dense_rank()over

(partition

by

deptno

order

by

sal)

r

from

scott.emp

t

where

deptno=30)

where

r<=3

4、select

*

from(select

t.*,rank()over

(partition

by

n

order

by

sal)

r

from

(select

''

as

n,tt.*

from

scott.emp

tt)

t)

where

r

between

5

and

10

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