SQL语句性能
-- 样例1
select t3.*,t4.emplname from (
?????? select t2.*,rownum rn from (
????????????? select t.* from t_mcs_mmsinfo t order by t.taskreqtime desc
?????? ) t2
) t3
left join t_mcs_user t4 on t3.assessorid = t4.userid
where t3.rn > 0 and t3.rn < 100;
-- 样例2
select t4.*,t5.emplname from (
???? select * from (
??????????? select t2.*,rownum rn from (
?????????????????? select t.* from t_mcs_mmsinfo t order by t.taskreqtime desc
??????????? ) t2
???? ) t3
where t3.rn > 0 and t3.rn < 100
) t4
left join t_mcs_user t5 on t4.assessorid = t5.userid;
?
测试结果：上述两SQL语句，执行的时间相同；
结论：在进行表连接时，where条件将优先被执行；
?
欢迎拍砖和纠正，相互学习
