full join ,left join ,right join,inner join
一、full join
----- full join
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A
FULL JOIN (SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
ON A.T1 = B.T1
二、left join
---- left join
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A
LEFT JOIN (SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
ON A.T1 = B.T1
----相當于
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A,
(SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
WHERE A.T1 = B.T1(+)
三、rightjoin
---- right join
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A
RIGHT JOIN (SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
ON A.T1 = B.T1
----相當于
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A,
(SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
WHERE A.T1(+) = B.T1
四、inner join
---- inner join
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A
INNER JOIN (SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
ON A.T1 = B.T1
----相當于
SELECT A.*, B.*
FROM (SELECT 0 AS T1
FROM DUAL
UNION
SELECT 1 AS T1
FROM DUAL
UNION
SELECT 2 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) A,
(SELECT 4 AS T1
FROM DUAL
UNION
SELECT 3 AS T1 FROM DUAL) B
WHERE A.T1 = B.T1
本文來自部落格園,作者:農碼一生,轉載請注明原文連結:https://www.cnblogs.com/wml-it/p/13650610.html
技術的發展日新月異,随着時間推移,無法保證本部落格所有内容的正确性。如有誤導,請大家見諒,歡迎評論區指正! 個人開源代碼連結: GitHub:https://github.com/ITMingliang
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