zuo0209
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#交叉连接CROSS JOIN 又称为笛卡尔积
SELECT student.*,score.* FROM student, score
SELECT student.*,score.* FROM student CROSS JOIN score
#内连接 INNER可省略
SELECT stu.*,score.* FROM student stu,score WHERE
stu.id = score.stu_id
SELECT stu.*,score.* FROM student stu INNER JOIN score ON
stu.id = score.stu_id
#左外连接 左 ...