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
- 语法
SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key
SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key WHERE B.Key IS NULL
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图示
RIGHT JOIN
- 语法
SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key
SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key WHERE A.Key IS NULL
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图示
INNER JOIN
- 语法
select_list] FROM TableA A INNER JOIN TableB B ON A.Key=B.Key
-
图示
FULL JOIN
- 语法
SELECT [select_list] FROM TableA A FULL OUTER JOIN TableB B ON A.Key=B.Key
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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图示
更多信息，参考：