摘要:
一、EXISTS 并非总比IN 快,究竟应该选用 IN 还是 EXISTS ,可参考以下分析:1、Select * from t1 where x in ( select y from t2 )相当于select * from t1, ( select distinct y from t2 ) t2 where t1.x = t2.y; 2、select * from t1 where exi... 阅读全文
雪山之巅的阳光冰雪天地的清冷,超凡脱俗的时空,一缕色彩,点缀在清蓝的背景中....那就是——雪山之巅的阳光 |