62. 解释一下MySQL中内连接，外连接等的区别（MySQL面试第五弹）

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 <select_list> 
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
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2.LEFT JOIN（左连接）

SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
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3.RIGHT JOIN（右连接）

SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
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4.OUTER JOIN（外连接）

SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
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5.LEFT JOIN EXCLUDING INNER JOIN（左连接-内连接）

SELECT <select_list> 
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL
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6.RIGHT JOIN EXCLUDING INNER JOIN（右连接-内连接）

SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL
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7.OUTER JOIN EXCLUDING INNER JOIN（外连接-内连接）

SELECT <select_list>
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

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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