delete 与 delete from 有区别吗

[crazyleeyang]

rt

[dawugui]

如果涉及到子查询,有区别,如果单表简单操作,无区别.

delete tb where ...
delete from tb where...

delete tb where not exists(...) --错误
delete tb from tb t where not exists(...) --正确.

[luoyoumou]

-- 一般习惯用 delete from ，这样写更让人容易理解!

-- 当然：没有区别!
sys@TBWORA> conn scott/bee56915
已连接。
scott@TBWORA> delete emp;

已删除5行。

scott@TBWORA> delete from emp;

已删除0行。

scott@TBWORA> delete emp2;

已删除0行。

scott@TBWORA> delete from emp2;

已删除0行。

scott@TBWORA> delete emp2 where deptno=30;

已删除0行。

[luoyoumou]

[Quote=引用 1 楼 dawugui 的回复:]

如果涉及到子查询,有区别,如果单表简单操作,无区别.

delete tb where ...
delete from tb where...

delete tb where not exists(...) --错误
delete tb from tb t where not exists(...) --正确.
[/Quote]

-- 1楼说的这种情况应该不存在：

scott@TBWORA> delete emp where not exists (select 1 from dept where dept.dname='LUOYOUMOU' and dept.deptno=emp.deptno);

已删除5行。

scott@TBWORA> rollback;

回退已完成。

scott@TBWORA> delete from emp where not exists (select 1 from dept where dept.dname='LUOYOUMOU' and dept.deptno=emp.deptno);

已删除5行。

scott@TBWORA> rollback;

回退已完成。

scott@TBWORA> delete emp where not exists (select 1 from dept where dept.dname='RESEARCH' and dept.deptno=emp.deptno);

已删除0行。

scott@TBWORA> delete from emp where not exists (select 1 from dept where dept.dname='RESEARCH' and dept.deptno=emp.deptno);

已删除0行。

[luoyoumou]

-- 纠正一下：对于Oracle来说， 1楼说的这种情况应该不存在!

[dawugui]

[Quote=引用 4 楼 luoyoumou 的回复:]
-- 纠正一下：对于Oracle来说， 1楼说的这种情况应该不存在!
[/Quote]原来如此.

[crazyleeyang]

好的，多谢3楼，请接分