Mysql将列转换为行（数据透视表）

I have a table like this

我有一张这样的桌子

+---+-----+----+----+----+----+
|id |month|col1|col2|col3|col4|
+---+-----+----+----+----+----+
|101|Jan  |A   |B   |NULL|B   |
+---+-----+----+----+----+----+
|102|feb  |C   |A   |G   |E   |
+---+-----+----+----+----+----+

And then I want to create report like this

然后我想创建这样的报告

+----+---+---+
|desc|jan|feb|
+----+---+---+
|col1|A  |C  |
+----+---+---+
|col2|B  |A  |
+----+---+---+
|col3|0  |G  |
+----+---+---+
|Col4|B  |E  |
+----+---+---+

Can anyone help with this?

有人能帮忙吗？

1 个解决方案

#1

What you need to do is first, unpivot the data and then pivot it. But unfortunately MySQL does not have these functions so you will need to replicate them using a UNION ALL query for the unpivot and an aggregate function with a CASE for the pivot.

您需要做的是首先，取消数据转换然后转动数据。但遗憾的是MySQL没有这些功能，所以你需要使用UNION ALL查询来复制它们，而使用带有CASE的聚合函数来实现枢轴。

The unpivot or UNION ALL piece takes the data from your col1, col2, etc and turns it into multiple rows:

unpivot或UNION ALL部分从col1，col2等获取数据并将其转换为多行：

select id, month, col1 value, 'col1' descrip
from yourtable
union all
select id, month, col2 value, 'col2' descrip
from yourtable
union all
select id, month, col3 value, 'col3' descrip
from yourtable
union all
select id, month, col4 value, 'col4' descrip
from yourtable

See SQL Fiddle with Demo.

请参阅SQL Fiddle with Demo。

Result:

结果：

|  ID | MONTH |  VALUE | DESCRIP |
----------------------------------
| 101 |   Jan |      A |    col1 |
| 102 |   feb |      C |    col1 |
| 101 |   Jan |      B |    col2 |
| 102 |   feb |      A |    col2 |
| 101 |   Jan | (null) |    col3 |
| 102 |   feb |      G |    col3 |
| 101 |   Jan |      B |    col4 |
| 102 |   feb |      E |    col4 |

You then wrap this in a subquery to apply the aggregate and the CASE to convert this into the format you want:

然后将其包装在子查询中以应用聚合和CASE将其转换为您想要的格式：

select descrip, 
  max(case when month = 'jan' then value else 0 end) jan,
  max(case when month = 'feb' then value else 0 end) feb
from
(
  select id, month, col1 value, 'col1' descrip
  from yourtable
  union all
  select id, month, col2 value, 'col2' descrip
  from yourtable
  union all
  select id, month, col3 value, 'col3' descrip
  from yourtable
  union all
  select id, month, col4 value, 'col4' descrip
  from yourtable
) src
group by descrip

See SQL Fiddle with demo

请参阅SQL Fiddle with demo

The result is:

结果是：

| DESCRIP | JAN | FEB |
-----------------------
|    col1 |   A |   C |
|    col2 |   B |   A |
|    col3 |   0 |   G |
|    col4 |   B |   E |

#1