作者:C.L. Moffatthttp://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins
下圖展示了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相關的 7 種用法。
具體分解如下:
1.INNER JOIN(內連接)
SELECT <select>
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
/<select>
2.LEFT JOIN(左連接)
SELECT <select>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
/<select>
3.RIGHT JOIN(右連接)
SELECT <select>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
/<select>
4.OUTER JOIN(外連接)
SELECT <select>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
/<select>
5.LEFT JOIN EXCLUDING INNER JOIN(左連接-內連接)
SELECT <select>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL
/<select>
6.RIGHT JOIN EXCLUDING INNER JOIN(右連接-內連接)
SELECT <select>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL
/<select>
7.OUTER JOIN EXCLUDING INNER JOIN(外連接-內連接)
SELECT <select>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL OR B.Key IS NULL
/<select>
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