MySQL从表中选择一个字段WHERE条件是多行

Question

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

Answer 1

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. (eg there is a PK on id, keyword )

Answer 2

SELECT DISTINCT id FROM table
WHERE 
(keyword="display" and value=15.6) OR (keyword="harddrive" and value=320)