Question

抱歉，我应该更具体地回答我的问题：

这是我当前的问题

我有一张桌子，上面有：

Customer_ID        H2_1      H2_2      H2_3     H2_4      H2_5
123                 7         3         13       5         2
456                 7         3         13       5         2
789                 7         3         13       5         2

我需要它看起来像这样：

Customer_ID         H2_Code
123                    7
123                    3
123                   13
123                    5
123                    2
456                    7
456                    3
456                   13
456                    5
456                    2
789                    7
789                    3
789                   13
789                    5

Answer 1

您需要UNION ALL来组合所有列：

SELECT Customer_ID, H2_1 AS H2_Code
FROM table t
UNION ALL
SELECT Customer_ID, H2_2
FROM table t
UNION ALL
SELECT Customer_ID, H2_3
FROM table t 
UNION ALL
SELECT Customer_ID, H2_4
FROM table t 
UNION ALL
SELECT Customer_ID, H2_5
FROM table t

Answer 2

您似乎想要union all：

select Customer_ID, H2_1 as h2_code from t
union all
select Customer_ID, H2_2 as h2_code from t
union all
select Customer_ID, H2_3 as h2_code from t
union all
select Customer_ID, H2_4 as h2_code from t
union all
select Customer_ID, H2_5 as h2_code from t;

请注意，union all需要扫描表格5次。对于中小型表，这不是问题。对于较大的表，有一些稍微复杂的机制，它们只会扫描一次表。

Answer 3

您可能希望合并获取每个H2_something的不同查询，然后按customer_id进行订购

模式（MySQL v5.7）

CREATE TABLE tableName (
  `Customer_ID` INTEGER,
  `H2_1` INTEGER,
  `H2_2` INTEGER,
  `H2_3` INTEGER,
  `H2_4` INTEGER,
  `H2_5` INTEGER
);

INSERT INTO tableName
  (`Customer_ID`, `H2_1`, `H2_2`, `H2_3`, `H2_4`, `H2_5`)
VALUES
  ('123', '7', '3', '13', '5', '2'),
  ('456', '7', '3', '13', '5', '2'),
  ('789', '7', '3', '13', '5', '2');

查询＃1

SELECT customer_Id, H2_1 AS H2_Code FROM tableName
UNION ALL
SELECT customer_Id, H2_2 FROM tableName
UNION ALL
SELECT customer_Id, H2_3 FROM tableName
UNION ALL
SELECT customer_Id, H2_4 FROM tableName
UNION ALL
SELECT customer_Id, H2_5 FROM tableName
ORDER BY customer_Id;

| customer_Id | H2_Code |
| ----------- | ------- |
| 123         | 3       |
| 123         | 13      |
| 123         | 5       |
| 123         | 2       |
| 123         | 7       |
| 456         | 3       |
| 456         | 13      |
| 456         | 5       |
| 456         | 2       |
| 456         | 7       |
| 789         | 7       |
| 789         | 3       |
| 789         | 13      |
| 789         | 5       |
| 789         | 2       |

View on DB Fiddle

Answer 4

请注意，规范化的架构通常看起来像这样：

Customer_ID    H2    val    
123             1      7     
123             2      3     
123             3     13     
123             4      5     
123             5      2
456             1      7     
456             2      3     
456             3     13     
456             4      5     
456             5      2
789             1      7     
789             2      3     
789             3     13     
789             4      5     
789             5      2

我想创建一个表，该表具有相同属性的多个行，但具有不同的列

4 个答案: