作者：C.L. Moffatt
http://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins
7種 join 用法
1.INNER JOIN（內連接）
SELECT <select_list>
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
2.LEFT JOIN（左連接）
SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
3.RIGHT JOIN（右連接）
SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
4.OUTER JOIN（外連接）
SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
5.LEFT JOIN EXCLUDING INNER JOIN （左連接-排除內連接）
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 （右連接-排除內連接）
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 （外連接-排除內連接）
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