- INNER JOIN 交叉關(guān)聯(lián)
-- 返回兩個(gè)表連接字段相等的行
SELECT * FROM 表1 INNER JOIN 表2 ON 表1.字段=表2.字段;
- LEFT JOIN 左關(guān)聯(lián)
-- 返回左表中所有記錄和右表中連接字段相等的行
SELECT * FROM 表1 LEFT JOIN 表2 ON 表1.字段=表2.字段;
- RIGHT JOIN 右關(guān)聯(lián)
-- 返回右表中所有記錄和左表中連接字段相等的行
SELECT * FROM 表1 RIGHT JOIN 表2 ON 表1.字段=表2.字段;
-- 3 表連接查詢(xún)
SELECT a.Name,b.Subject,c.Score FROM Student as a
INNER JOIN Score as c ON a.ID=c.StudentID
INNER JOIN Subject as b ON b.ID=c.SubjectID;
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SELECT * FROM Student a INNER JOIN Score b ON a.id=b.StudentID;
SELECT * FROM Student a LEFT JOIN Score b ON a.id=b.StudentID;
SELECT * FROM Student a RIGHT JOIN Score b ON a.id=b.StudentID;
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