如何在 MySQL 的 CONCAT 中使用 GROUP_CONCAT

2021-11-20 00:00:00 concat mysql group-concat

如果我在 MySQL 中有一个包含以下数据的表:

If I have a table with the following data in MySQL:

id       Name       Value
1          A          4
1          A          5
1          B          8
2          C          9

如何将其转换为以下格式?

how do I get it into the following format?

id         Column
1          A:4,5,B:8
2          C:9


我想我必须使用 GROUP_CONCAT.但我不确定它是如何工作的.


I think I have to use GROUP_CONCAT. But I'm not sure how it works.

推荐答案

select id, group_concat(`Name` separator ',') as `ColumnName`
from
(
  select 
    id, 
    concat(`Name`, ':', group_concat(`Value` separator ',')) as `Name`
  from mytbl
  group by 
    id, 
    `Name`
) tbl
group by id;

你可以在这里看到它的实现:Sql Fiddle Demo.正是您所需要的.

You can see it implemented here : Sql Fiddle Demo. Exactly what you need.

更新分两步拆分.首先，我们得到一个表，其中包含针对唯一 [Name,id] 的所有值(逗号分隔).然后从获得的表中，我们将所有名称和值作为针对每个唯一 id 的单个值请参阅此处的说明 SQL Fiddle Demo(向下滚动有两个结果集)

Update Splitting in two steps. First we get a table having all values(comma separated) against a unique[Name,id]. Then from obtained table we get all names and values as a single value against each unique id See this explained here SQL Fiddle Demo (scroll down as it has two result sets)

编辑 阅读问题时出错，我仅按 id 分组.但是如果(值要按名称和 id 分组，然后按 id 分组)，则需要两个 group_contacts.以前的答案是

Edit There was a mistake in reading question, I had grouped only by id. But two group_contacts are needed if (Values are to be concatenated grouped by Name and id and then over all by id). Previous answer was

select 
id,group_concat(concat(`name`,':',`value`) separator ',')
as Result from mytbl group by id

你可以在这里看到它的实现:SQL Fiddle Demo

You can see it implemented here : SQL Fiddle Demo

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