Mysql filter (AND) query on multiple fields in multiple joined rows

问题

I have created a query which returns a list of products with their fields and values. Now I want to search through fields for a certain value and get a resultlist matching this search query. The problem is that I want an AND construction, so fieldx value must be like %car% and fieldy value must be like %chrome%.

Here`s an example of my query and the resultset:

Query

SELECT p.id as product,pf.field_name,pfv.field_value
FROM product p
JOIN field pf ON pf.product_id = p.product_id
JOIN field_val pfv ON pfv.field_id = pf.field_id

Resultset

product | field_name | field_value
pr1     | meta_title | Example text
pr1     | meta_kw    | keyword,keyword1
pr1     | prod_name  | Product 1
pr2 ....

So with the above query and resultset in mind I want to do the following: Query all products where meta_title contains 'Example' and where prod_name contains 'Product'. After that, I want to group the results so that only products are returned where both search queries matches.

I tried everything I could think off and I have tried many solutions on kind of the same questions, but I think mine is different because I need the AND match on the field name as well the value over multiple rows.

For example, I tried adding this as WHERE clause:

WHERE
(field_name = 'meta_title' AND field_value LIKE '%Example%') AND 
(field_name = 'prod_name' AND field_value LIKE '%Product%')

Obviously this won`t work because after the first where on meta_title there is no result left for other field names. But changing the WHERE to OR would not give me the desired result.

I also tried with HAVING but seems like same result.

Anyone an idea how to solve this, or is this just not possible?

回答1:

A relatively simple way to do this is to use group by and having:

SELECT p.id as product
FROM product p JOIN
     field pf
     ON pf.product_id = p.product_id JOIN
     field_val pfv
     ON pfv.field_id = pf.field_id
WHERE (field_name = 'meta_title' AND field_value LIKE '%Example%') OR 
      (field_name = 'prod_name' AND field_value LIKE '%Product%')
GROUP BY p.id
HAVING COUNT(DISTINCT field_name) = 2;

By modifying the HAVING clause (and perhaps removing the WHERE), it is possible to express lots of different logic for the presence and absence of different fields. For instance > 0 would be OR, and = 1 would be one value or the other, but not both.

回答2:

Try this:

select product from [table_name]
    WHERE field_name like 'meta_title' AND field_value LIKE '%Example%'

UNION

select product from [table_name]
    WHERE field_name like 'prod_name' AND field_value LIKE '%Product%'

回答3:

First: I would go for the easiest way. If Prerak Solas solution works and the performance is OK for you, go for it.

An other solution is to use a pivot table. With this the select of your table would return something like this:

product | meta_title   | meta_kw          | prod_name
pr1     | Example text | keyword,keyword1 | Product 1
pr2 ...

You could than easily query like:

SELECT 
  p.Id 
FROM 
  (subquery/view) 
WHERE 
  meta_title LIKE '%Example%' AND 
  prod_name LIKE '%Product%'

For more infos about pivot read this

来源：https://stackoverflow.com/questions/31289707/mysql-filter-and-query-on-multiple-fields-in-multiple-joined-rows

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mysql

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join

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