mysql-joins具体用法说明

TABLE_A										|		 TABLE_B
 PK Value     	 				|   PK Value
---- ----------    				|   ---- ----------
 1 FOX     				|   1 TROT
 2 COP     				|   2 CAR
 3 TAXI     				|   3 CAB
 6 WASHINGTON    				|   6 MONUMENT
 7 DELL     				|   7 PC
 5 ARIZONA    				|   8 MICROSOFT
 4 LINCOLN    				|   9 APPLE
 10 LUCENT     				|   11 SCOTCH

join_table:
 table_reference JOIN table_factor [join_condition]											//内连接
 | table_reference {LEFT|RIGHT|FULL} [OUTER] JOIN table_reference join_condition				//外连接
 | table_reference LEFT SEMI JOIN table_reference join_condition								//左半连接
 | table_reference CROSS JOIN table_reference [join_condition] (as of Hive 0.10)


table_reference:
 table_factor					//表
 | join_table						//join语句


table_factor:
 tbl_name [alias]				//表名[别名]
 | table_subquery alias			//子查寻[别名]
 | ( table_references )			//带空号的table_reference


join_condition:
 ON expression					//on开头的条件语句

SELECT <select_list> 
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key

-- Inner JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
  B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
INNER JOIN Table_B B
ON A.PK = B.PK

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
 1 FOX  TROT   1
 2 COP  CAR   2
 3 TAXI  CAB   3
 6 WASHINGTON MONUMENT  6
 7 DELL  PC   7

(5 row(s) affected)

SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key

-- Left JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
LEFT JOIN Table_B B
ON A.PK = B.PK

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
 1 FOX  TROT   1
 2 COP  CAR   2
 3 TAXI  CAB   3
 4 LINCOLN NULL  NULL
 5 ARIZONA NULL  NULL
 6 WASHINGTON MONUMENT  6
 7 DELL  PC   7
 10 LUCENT  NULL  NULL

(8 row(s) affected)

SELECT <select_list> 
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL

-- Left Excluding JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
LEFT JOIN Table_B B
ON A.PK = B.PK
WHERE B.PK IS NULL

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
 4 LINCOLN NULL  NULL
 5 ARIZONA NULL  NULL
 10 LUCENT  NULL  NULL
(3 row(s) affected)

SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key

-- Right JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
RIGHT JOIN Table_B B
ON A.PK = B.PK

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
 1 FOX  TROT   1
 2 COP  CAR   2
 3 TAXI  CAB   3
 6 WASHINGTON MONUMENT  6
 7 DELL  PC   7
NULL NULL  MICROSOFT  8
NULL NULL  APPLE   9
NULL NULL  SCOTCH  11

(8 row(s) affected)

SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL

-- Right Excluding JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
RIGHT JOIN Table_B B
ON A.PK = B.PK
WHERE A.PK IS NULL

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
NULL NULL  MICROSOFT  8
NULL NULL  APPLE   9
NULL NULL  SCOTCH  11

(3 row(s) affected)

SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key

-- Outer JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.PK = B.PK

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
 1 FOX  TROT   1
 2 COP  CAR   2
 3 TAXI  CAB   3
 6 WASHINGTON MONUMENT  6
 7 DELL  PC   7
NULL NULL  MICROSOFT  8
NULL NULL  APPLE   9
NULL NULL  SCOTCH  11
 5 ARIZONA NULL  NULL
 4 LINCOLN NULL  NULL
 10 LUCENT  NULL  NULL

(11 row(s) affected)

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

-- Outer Excluding JOIN
SELECT A.PK AS A_PK, A.Value AS A_Value,
B.Value AS B_Value, B.PK AS B_PK
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.PK = B.PK
WHERE A.PK IS NULL
OR B.PK IS NULL

A_PK A_Value B_Value B_PK
---- ---------- ---------- ----
NULL NULL  MICROSOFT  8
NULL NULL  APPLE   9
NULL NULL  SCOTCH  11
 5 ARIZONA NULL  NULL
 4 LINCOLN NULL  NULL
 10 LUCENT  NULL  NULL

(6 row(s) affected)