sqljoin使用场景(一张图看懂SQL的各种)
下图展示了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相关的 7 种用法。
具体分解如下:
1.INNER JOIN(内连接)
SELECT
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
2.LEFT JOIN(左连接)
SELECT
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
3.RIGHT JOIN(右连接)
SELECT
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
4.OUTER JOIN(外连接)
SELECT
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
5.LEFT JOIN EXCLUDING INNER JOIN(左连接-内连接)
SELECT
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL
6.RIGHT JOIN EXCLUDING INNER JOIN(右连接-内连接)
SELECT
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL
7.OUTER JOIN EXCLUDING INNER JOIN(外连接-内连接)
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
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