要想面对一个新的开始,一个人必须有幻想、有心愿、有对将来的神往。如果没有这些,就不叫新的开始,而叫流亡。
下图展现了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相干的 7 种用法。
具体合成如下:
1.INNER JOIN(内连贯)
SELECT <select_list>
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
2.LEFT JOIN(左连贯)
SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
3.RIGHT JOIN(右连贯)
SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
4.OUTER JOIN(外连贯)
SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
5.LEFT JOIN EXCLUDING INNER JOIN(左连贯 - 内连贯)
SELECT <select_list>
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(右连贯 - 内连贯)
SELECT <select_list>
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(外连贯 - 内连贯)
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