MySQL 从表中选择一个字段 WHERE 条件在多行中-数据库问题

MySQL select one field from table WHERE condition is in multiple rows(MySQL 从表中选择一个字段 WHERE 条件在多行中)

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问题描述

试图找到答案，但还是找不到..表格如下:

<上一页>id、关键字、值1 显示 15.61个硬盘3201 公羊 3

所以我需要的是这样的.. 从这个表中选择一个 ID，其中 (keyword="display" and value="15.6") AND (keyword="harddrive" and value="320")也有可能会有 3 或 4 个这样的关键字条件导致返回一个 id(一行)

似乎有一些东西要处理UNION，但我之前没有使用它，所以我无法弄清楚

提前致谢

解决方案

这是一个关系除法问题.像下面这样的东西应该可以做到.

选择 idFROM your_table在哪里(keyword="display" and value="15.6") OR (keyword="harddrive" and value="320")按 ID 分组有计数(*)= 2

我假设您的表具有适当的约束，因此不可能有完全重复的行.(例如id,keyword上有PK)

Tried to find the answer, but still couldn't.. The table is as follows:

id, keyword,   value
1   display    15.6
1   harddrive  320
1   ram        3

So what i need is something like this.. Select an id from this table where (keyword="display" and value="15.6") AND (keyword="harddrive" and value="320") There's also a possibility that there will be 3 or 4 such keyword conditions which should result into returning one id (one row)



It seems there's something to deal with UNION but i didn't use it before so i can't figure it out

Thanks in advance
 解决方案 
This is a relational division problem. Something like the following should do it.
SELECT id
FROM your_table
WHERE 
(keyword="display" and value="15.6") OR (keyword="harddrive" and value="320")
GROUP BY id
HAVING COUNT(*) = 2
I'm assuming that your table has appropriate constraints such that it is impossible for there to be a completely duplicated row.  (e.g. there is a PK on id, keyword)

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