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