sql 左连接

以前的写法： SELECT stu.*, sc.C,sc.score FROM student stu,sc sc1,sc sc2,sc sc WHERE stu.S = sc.s AND stu.S = sc1.S AND stu.S = sc2.S AND sc1.C = '01' AND sc2.C = '02' AND sc1.score > sc2.score 现在的写法： select

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