JOIN¶
语法说明¶
JOIN 用于把来自两个或多个表的行结合起来。
下图展示了 LEFT JOIN、RIGHT JOIN、INNER JOIN、和 OUTER JOIN。
LEFT JOIN
SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key |
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SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key WHERE B.Key IS NULL |
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RIGHT JOIN
SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key |
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SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key WHERE A.Key IS NULL |
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INNER JOIN
SELECT [select_list] FROM TableA A INNER JOIN TableB B ON A.Key=B.Key |
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FULL JOIN
SELECT [select_list] FROM TableA A FULL OUTER JOIN TableB B ON A.Key=B.Key |
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SELECT [select_list] FROM TableA A FULL OUTER JOIN TableB B ON A.Key=B.Key WHERE A.Key IS NULL OR B.Key IS NULL |
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更多信息，参考：