--1.查找到同時存在" 01 "課程和" 02 "課程的情況

-- 創建表及數據信息,在第一篇隨筆中.

-- 1.通過兩張子表得到課程01和課程02的成績信息，

 

-- 2.笛卡兒積合並兩張表，最后WHERE篩選

SELECT * 
FROM (SELECT * FROM sc WHERE Cid = 01) AS a,(SELECT * FROM sc WHERE Cid = 02) AS b 
WHERE a.Sid = b.SId;

 -- 3.去除冗余;

SELECT a.Sid,a.score 01_score,b.score 02_score
FROM (SELECT * FROM sc WHERE Cid = 01) AS a,(SELECT * FROM sc WHERE Cid = 02) AS b 
WHERE a.Sid = b.Sid ;