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INNER JOIN
Детально о JOIN в SQL
23 августа 2016, 15:56
Рассмотрим 7 типов join:
- INNER JOIN
- LEFT JOIN
- RIGHT JOIN
- FULL OUTER JOIN (в MySQL UNION)
- LEFT JOIN EXCLUDING INNER JOIN
- RIGHT JOIN EXCLUDING INNER JOIN
- OUTER JOIN EXCLUDING INNER JOIN
Наглядно посмотрим в чем разница.
![](/blog/pictures/Visual_SQL_JOINS_V2.png)
А теперь подробно о каждом из них.
Inner JOIN
![](/blog/pictures/INNER_JOIN.png)
SELECT <select_list>
FROM Table_A A
INNER JOIN Table_B B
ON A.Key = B.Key
Left JOIN
![](/blog/pictures/LEFT_JOIN.png)
SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
Right JOIN
![](/blog/pictures/RIGHT_JOIN.png)
SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
Outer JOIN
![](/blog/pictures/FULL_OUTER_JOIN.png)
SELECT <select_list>
FROM Table_A A
FULL OUTER JOIN Table_B B
ON A.Key = B.Key
Left Excluding JOIN
![](/blog/pictures/LEFT_EXCLUDING_JOIN.png)
SELECT <select_list>
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL
Right Excluding JOIN
![](/blog/pictures/RIGHT_EXCLUDING_JOIN.png)
SELECT <select_list>
FROM Table_A A
RIGHT JOIN Table_B B
ON A.Key = B.Key
WHERE A.Key IS NULL
Outer Excluding JOIN
![](/blog/pictures/OUTER_EXCLUDING_JOIN.png)
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
А теперь все это на примере 2 простых таблиц из БД:
TABLE_A
PK Value
---- ----------
1 FOX
2 COP
3 TAXI
6 WASHINGTON
7 DELL
5 ARIZONA
4 LINCOLN
10 LUCENT
TABLE_B
PK Value
---- ----------
1 TROT
2 CAR
3 CAB
6 MONUMENT
7 PC
8 MICROSOFT
9 APPLE
11 SCOTCH
-- 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)
-- 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)
-- 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)
-- 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)
-- 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)
-- 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)
-- 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)
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