MySQL从多个表中选择条件

时间:2012-04-27 14:39:41

标签: mysql

我有4张桌子:

  • ARTICOLE
  • BAR
  • BUCATARIE
  • MAGAZIE

的MySQL> select * from ARTICOLE;

| OID | ART      |  
|   1 | TEST     |
|   2 | TESTQ    |
|   3 | MYART    |
|   4 | MYARTBUC |

4行(0.00秒)

的MySQL> select * from BAR;

| OID | ART   | CANT     |
|   1 | TEST  |  3.00000 |
|   2 | TESTQ |  1.00000 |
|   3 | MYART | 20.00000 |

3行(0.00秒)

的MySQL> select * from BUCATARIE;

| OID | ART      | CANT     |
|   1 | TEST     |  5.00000 |
|   2 | MYARTBUC | 10.00000 |

2行(0.00秒)

的MySQL> select * from MAGAZIE; 空集(0.00秒)

以下查询

的MySQL> select a.ART,sum(bar.CANT),sum(buc.CANT),sum(mag.CANT) from ARTICOLE a,BUCATARIE buc,BAR bar,MAGAZIE mag where a.ART=bar.ART and a.ART=bar.ART and a.ART=mag.ART group by a.ART;

返回:


空集(0.00秒)

如何返回查询:

| ART | sum(bar.CANT) | sum(buc.CANT) | sum(mag.CANT) |
TEST  |  3.00000 | 5.00000 | NULL |
TESTQ |  1.00000 | NULL | NULL |
MYART | 20.00000 | NULL | NULL|
MYARTBUC | NULL | 10.00000 | NULL |

????

任何帮助表示感谢。

1 个答案:

答案 0 :(得分:1)

您需要使用LEFT JOIN来包含其他表的结果,而不会过滤掉不匹配的记录:

   select a.ART,sum(bar.CANT),sum(buc.CANT),sum(mag.CANT)
     from ARTICOLE a
left join BUCATARIE buc on buc.ART = a.ART
left join BAR bar on bar.ART = a.ART
left join MAGAZIE mag on mag.ART = a.ART
group by a.ART;

示例结果:

ART         SUM(BAR.CANT)   SUM(BUC.CANT)   SUM(MAG.CANT)
MYART       20      
MYARTBUC                    10  
TEST        3               5   
TESTQ       1       

演示:http://www.sqlfiddle.com/#!2/6efb2/2