这些是我的表格;
mysql> show tables;
+--------------------+
| Tables_in_products |
+--------------------+
| main_info |
| product1 |
| product2 |
+--------------------+
3 rows in set (0.00 sec)
这是我的第一张表
mysql> select * from main_info;
+------+------+-------+-------+----------+
| key1 | key2 | info1 | info2 | date |
+------+------+-------+-------+----------+
| 1 | 1 | 15 | 90 | 20120501 |
| 1 | 2 | 14 | 92 | 20120601 |
| 1 | 3 | 15 | 82 | 20120801 |
| 2 | 1 | 17 | 90 | 20130302 |
| 2 | 2 | 16 | 88 | 20130601 |
+------+------+-------+-------+----------+
5 rows in set (0.00 sec)
这是产品表1：
mysql> select * from product1;
+------+------+--------+--------------+
| key1 | key2 | serial | product_data |
+------+------+--------+--------------+
| 1 | 1 | 0 | 15.556 |
| 1 | 1 | 1 | 14.996 |
| 1 | 1 | 2 | 12.556 |
| 1 | 1 | 3 | 15.669 |
| 1 | 2 | 0 | 12.556 |
| 1 | 2 | 1 | 13.335 |
| 1 | 3 | 1 | 12.225 |
| 1 | 3 | 2 | 13.556 |
| 1 | 3 | 3 | 14.556 |
| 2 | 1 | 0 | 12.556 |
| 2 | 1 | 1 | 13.553 |
| 2 | 1 | 2 | 12.335 |
+------+------+--------+--------------+
12 rows in set (0.00 sec)
这是第二个产品表
mysql> select * from product2;
+------+------+--------+--------------+
| key1 | key2 | serial | product_data |
+------+------+--------+--------------+
| 1 | 1 | 0 | 5.556 |
| 1 | 1 | 1 | 4.996 |
| 1 | 2 | 0 | 2.556 |
| 1 | 2 | 1 | 3.335 |
| 1 | 2 | 2 | 2.56 |
| 1 | 2 | 3 | 3.556 |
| 1 | 3 | 1 | 2.225 |
| 1 | 3 | 2 | 3.556 |
| 2 | 2 | 0 | 2.556 |
| 2 | 2 | 1 | 3.553 |
+------+------+--------+--------------+
10 rows in set (0.00 sec)
我有8个以上的产品表，我想在2个产品表和main_info表中比较key1, key2 and serial，具体取决于我想要合并的最大值，如果产品数据不存在则替换NaN最后希望得到1个输出，如下所示
预期的O / P
key1 key2 serial info1 info2 date product_table1_data product_table2_data
1 1 0 15 90 20120501 15.556 5.556
1 1 1 15 90 20120501 14.996 4.996
1 1 2 15 90 20120501 12.556 NaN
1 1 3 15 90 20120501 15.669 NaN
1 2 0 14 92 20120601 12.556 2.556
1 2 1 14 92 20120601 13.335 3.335
1 2 2 14 92 20120601 NaN 2.56
1 2 3 14 92 20120601 NaN 3.556
1 3 1 15 82 20120801 12.225 2.225
1 3 2 15 82 20120801 13.556 3.556
1 3 3 15 82 20120801 14.556 NaN
2 1 0 17 90 20130302 12.556 NaN
2 1 1 17 90 20130302 13.553 NaN
2 1 2 17 90 20130302 12.335 NaN
2 2 0 16 88 20130601 NaN 2.556
2 2 1 16 88 20130601 NaN 3.553
请有人帮助我获得预期的结果
这是我数据库的结构;
$ cat product.sql
--
-- Table structure for table `main_info`
--
DROP TABLE IF EXISTS `main_info`;
CREATE TABLE `main_info` (
`key1` varchar(1000) DEFAULT NULL,
`key2` varchar(1000) DEFAULT NULL,
`info1` varchar(1000) DEFAULT NULL,
`info2` varchar(1000) DEFAULT NULL,
`date` varchar(1000) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
LOCK TABLES `main_info` WRITE;
INSERT INTO `main_info` VALUES ('1','1','15','90','20120501'),('1','2','14','92','20120601'),('1','3','15','82','20120801'),('2','1','17','90','20130302'),('2','2','16','88','20130601');
UNLOCK TABLES;
DROP TABLE IF EXISTS `product1`;
CREATE TABLE `product1` (
`key1` varchar(1000) DEFAULT NULL,
`key2` varchar(1000) DEFAULT NULL,
`serial` varchar(1000) DEFAULT NULL,
`product_data` varchar(1000) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
LOCK TABLES `product1` WRITE;
INSERT INTO `product1` VALUES ('1','1','0','15.556'),('1','1','1','14.996'),('1','1','2','12.556'),('1','1','3','15.669'),('1','2','0','12.556'),('1','2','1','13.335'),('1','3','1','12.225'),('1','3','2','13.556'),('1','3','3','14.556'),('2','1','0','12.556'),('2','1','1','13.553'),('2','1','2','12.335');
UNLOCK TABLES;
DROP TABLE IF EXISTS `product2`;
CREATE TABLE `product2` (
`key1` varchar(1000) DEFAULT NULL,
`key2` varchar(1000) DEFAULT NULL,
`serial` varchar(1000) DEFAULT NULL,
`product_data` varchar(1000) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
LOCK TABLES `product2` WRITE;
INSERT INTO `product2` VALUES ('1','1','0','5.556'),('1','1','1','4.996'),('1','2','0','2.556'),('1','2','1','3.335'),('1','2','2','2.56'),('1','2','3','3.556'),('1','3','1','2.225'),('1','3','2','3.556'),('2','2','0','2.556'),('2','2','1','3.553');
UNLOCK TABLES;
我试过这个，但是这并没有考虑每个密钥对的序列最大值以及NaN
SELECT *
FROM main_info INNER JOIN product1
ON
main_info.key1=product1.key1 and
main_info.key2=product1.key2
INNER JOIN product2
ON
product1.key1=product2.key1 and
product1.key2=product2.key2
合并流程详情：回复评论
1。从main_info表中获取key1和key2 2。在表product1，product2中搜索，如果在表中的任何一个表或两个表中找到key1和key2，则获取这些键的串行列的长度，找到最大长度，
例如在product1表中，我们有4个序列号
+------+------+--------+--------------+
| key1 | key2 | serial | product_data |
+------+------+--------+--------------+
| 1 | 1 | 0 | 15.556 |
| 1 | 1 | 1 | 14.996 |
| 1 | 1 | 2 | 12.556 |
| 1 | 1 | 3 | 15.669 |
在第二个表中我们只有2个序列号，0和1只
+------+------+--------+--------------+
| key1 | key2 | serial | product_data |
+------+------+--------+--------------+
| 1 | 1 | 0 | 5.556 |
| 1 | 1 | 1 | 4.996 |
所以从表中合并序列号并检查数据是否存在（如果存在），然后保持product_date写入NaN
合并2个产品表时输出应该是这样的，一旦完成，添加对应于key1和key2的info1 info2和date列
+------+------+--------+--------------+--------------
| key1 | key2 | serial | product_data |product_data2
+------+------+--------+--------------+-------------
| 1 | 1 | 0 | 15.556 |5.556
| 1 | 1 | 1 | 14.996 |4.996
| 1 | 1 | 2 | 12.556 |NaN
| 1 | 1 | 3 | 15.669 |NaN
如果您需要更多信息，请与我们联系
谢谢。
答案 0 :(得分：1)
试试这个
SELECT * FROM ( SELECT main_info.* ,
product1.product_data as product_table1_data,
IF(product2.product_data IS NULL,"NaaN",
product2.product_data) as product_table2_data, product1.serial
FROM product1
LEFT JOIN product2 ON product1.key1 = product2.key1
AND product1.key2 = product2.key2
AND product1.serial=product2.serial
INNER JOIN main_info on
main_info.key1=product1.key1 and
main_info.key2=product1.key2
UNION
SELECT main_info.* ,
IF(product1.product_data IS NULL,"NaaN",product1.product_data) as product_table1_data,
product2.product_data as product_table2_data,
product2.serial
FROM product1 RIGHT JOIN product2 ON product1.key1 = product2.key1
AND product1.key2 = product2.key2
AND product1.serial=product2.serial
INNER JOIN main_info on
main_info.key1=product2.key1 and
main_info.key2=product2.key2) AS TEMP ORDER BY TEMP.key1,TEMP.key2,TEMP.serial
答案 1 :(得分：1)
试试这个
select T.key1,T.key2,T.serial,T.info1,T.info2,T.date,p1.product_data,p2.product_data
from
(SELECT m.key1 as key1,m.key2 as key2,m.info1 as info1,m.info2 as info2 ,m.date as date,p1.serial as serial
from main_info as m
join product1 as p1 on m.key1=p1.key1 and m.key2=p1.key2
union
SELECT m.key1 as key1,m.key2 as key2,m.info1 as info1,m.info2 as info2 ,m.date as date,p2.serial as serial
from main_info as m
join product2 as p2 on m.key1=p2.key1 and m.key2=p2.key2
) as T
left join product1 as p1 on T.key1=p1.key1 and T.key2=p1.key2 and p1.serial=T.serial
left join product2 as p2 on T.key1=p2.key1 and T.key2=p2.key2 and p2.serial=T.serial
修改 或
select T.key1,T.key2,T.serial,m.info1,m.info2,m.date,p1.product_data,p2.product_data
from
(SELECT p1.key1 as key1 ,p1.key2 as key2 ,p1.serial as serial
from product1 as p1
union
SELECT p2.key1 as key1,p2.key2 as key2,p2.serial as serial
from product2 as p2
) as T
left join product1 as p1 on T.key1=p1.key1 and T.key2=p1.key2 and p1.serial=T.serial
left join product2 as p2 on T.key1=p2.key1 and T.key2=p2.key2 and p2.serial=T.serial
left join main_info as m on T.key1=m.key1 and T.key2=m.key2