在MySQL中左連接查詢

我有兩個表。

doTable_1

+------+----------+ 
| AREA | REGISTER | 
+------+----------+ 
| AAAA | YS  | 
| BBBB | YS  | 
| CCCC | YS  | 
| DDDD | YS  | 
| EEEE | YS  | 
| FFFF | YS  | 
+------+----------+

doTable_2

+--------------+------+---------------+ 
| PREMIUM_AREA | AREA | NAME_AREA  | 
+--------------+------+---------------+ 
| ZZZ   | GGGG | AREA BLAWED | 
| ZZZ   | FFFF | AREA BAYWOOD | 
| ZZZ   | AAAA | AREA BILLFOLD | 
| ZZZ   | BBBB | AREA BEACHED | 
| ZZZ   | CCCC | AREA BASED | 
| ZZZ   | DDDD | AREA BANED | 
| ZZZ   | EEEE | AREA BAWD  | 
| ZZZ   | HHHH | AREA ARBORED | 
| ZZZ   | LLLL | AREA BLAND | 
| ZZZ   | MMMM | AREA YSENA | 
| ZZZ   | NNNN | AREA AIRSHED | 
| ZZZ   | PPPP | AREA ALLOD | 
| ZZZ   | QQQQ | AREA BEEYARD | 
+--------------+------+---------------+

我需要這個輸出，即連接兩個表的場區提取的所有行：

+------+--------------+----------+ 
| AREA | PREMIUM_AREA | REGISTER | 
+------+--------------+----------+ 
| AAAA | ZZZ   | YS  | 
| BBBB | ZZZ   | YS  | 
| CCCC | ZZZ   | YS  | 
| DDDD | ZZZ   | YS  | 
| EEEE | ZZZ   | YS  | 
| GGGG | ZZZ   | NULL  | 
| FFFF | ZZZ   | YS  | 
| HHHH | ZZZ   | NULL  | 
| LLLL | ZZZ   | NULL  | 
| MMMM | ZZZ   | NULL  | 
| NNNN | ZZZ   | NULL  | 
| PPPP | ZZZ   | NULL  | 
| QQQQ | ZZZ   | NULL  | 
+------+--------------+----------+

而且試過這個q uery但輸出錯誤，爲什麼？

mysql> SELECT 
    AREA, 
    PREMIUM_AREA, 
    REGISTER 
FROM 
    `doTable_1` A 
LEFT JOIN `doTable_2` CB ON A.AREA = CB.AREA 
WHERE 
    PREMIUM_AREA = 'ZZZ' 
GROUP BY 
    AREA 
ORDER BY 
    AREA ASC; 
+------+--------------+----------+ 
| AREA | PREMIUM_AREA | REGISTER | 
+------+--------------+----------+ 
| AAAA | ZZZ   | YS  | 
| BBBB | ZZZ   | YS  | 
| CCCC | ZZZ   | NULL  | 
| DDDD | ZZZ   | NULL  | 
| EEEE | ZZZ   | NULL  | 
| GGGG | ZZZ   | NULL  | 
| FFFF | ZZZ   | NULL  | 
| HHHH | ZZZ   | NULL  | 
| LLLL | ZZZ   | NULL  | 
| MMMM | ZZZ   | NULL  | 
| NNNN | ZZZ   | NULL  | 
| PPPP | ZZZ   | NULL  | 
| QQQQ | ZZZ   | NULL  | 
+------+--------------+----------+ 
14 rows in set

來源

2014-09-01 Antonio Mailtraq

提示：在select子句中寫入表名。 'A.Area，CB.premium_area，A.register'並嘗試沒有'Group BY' – diEcho 2014-09-01 10:18:00

你嘗試過的東西不能工作。你必須得到語法錯誤。 – Jens 2014-09-01 10:21:25

隨着LEFT JOIN，第一表必須包含要返回的所有行的一個，第二個表是可以缺少的行之一。因此，它應該是：

SELECT 
    A.AREA, 
    PREMIUM_AREA, 
    REGISTER 
FROM 
    `doTable_2` A 
LEFT JOIN `doTable_1` CB ON A.AREA = CB.AREA 
WHERE 
    PREMIUM_AREA = 'ZZZ' 
GROUP BY 
    A.AREA 
ORDER BY 
    A.AREA ASC;

DEMO

，你可以繼續以相同的順序表，並使用RIGHT JOIN。

來源

2014-09-01 10:18:04 Barmar

交換表的聯接子句中，像這樣的：

SELECT 
    AREA, 
    PREMIUM_AREA, 
    REGISTER 
FROM 
    `doTable_2` A 
LEFT JOIN `doTable_1` CB ON A.AREA = CB.AREA 
WHERE 
    PREMIUM_AREA = 'ZZZ' 
ORDER BY 
    AREA ASC;

來源

2014-09-01 10:18:35

可以使用right join

SELECT 
    AREA, 
    PREMIUM_AREA, 
    REGISTER 
FROM 
    `doTable_1` A 
RIGHT JOIN `doTable_2` CB ON A.AREA = CB.AREA 
WHERE 
    PREMIUM_AREA = 'ZZZ' 
GROUP BY 
    AREA 
ORDER BY 
    AREA ASC;

，或者如果你想使用left join交換表

SELECT 
    A.AREA, 
    PREMIUM_AREA, 
    REGISTER 
FROM 
    `doTable_2` A 
LEFT JOIN `doTable_1` CB ON A.AREA = CB.AREA 
WHERE 
    PREMIUM_AREA = 'ZZZ' 
GROUP BY 
    A.AREA 
ORDER BY 
    A.AREA ASC;

來源

2014-09-01 10:21:22

在MySQL中左連接查詢

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