MySQL 同表查询不同列

Question

I have two tables: Project and ProjectFieldValue

I am needing to return results from the ProjectFieldValue based on multiple different key/value options in the table. I can get it to work with one key/value pair, but once I add another AND statement to the query it returns nothing.

Here is a sample of my tables followed by my query...

Project Table

 ----------------------
 id | name
 ----------------------
 1  | Project #1

ProjectFieldValue Table

I have millions of records like this and they are all stored in this table and associated to a specific Project.

 ----------------------------------------------------------------------------------------
 id | project_id     | text_value      | date_value           | field_key
 ----------------------------------------------------------------------------------------
 1  | 1              | Active          | NULL                 | contract_status
 2  | 1              | NULL            | 2020-06-02 00:01:58  | listing_date
 3  | 1              | Seller          | NULL                 | contract_client_type
 4  | 1              | Active          | NULL                 | contract_option

Here are my queries broken down by what works and doesn't work:

This does work, but, it is searching on 1 key/value pair...

SELECT      p.name, p.id
FROM        ProjectFieldValue pfv
LEFT JOIN   Project p
 ON         pfv.project_id = p.id
WHERE       (pfv.text_value IN ( SELECT text_value FROM ProjectFieldValue WHERE text_value IN     ('Active')) AND field_key = 'contract_status')
GROUP BY    p.id

This doesn't work because it is searching on 3 key/value pairs...

SELECT      p.name, p.id
FROM        ProjectFieldValue pfv
LEFT JOIN   Project p
 ON         pfv.project_id = p.id
WHERE       (pfv.text_value IN ( SELECT text_value FROM ProjectFieldValue WHERE text_value IN ('Active')) AND field_key = 'contract_status')
AND         (pfv.text_value IN ( SELECT text_value FROM ProjectFieldValue WHERE text_value IN ('Seller')) AND field_key = 'contract_client_type')
AND         (pfv.date_value between '2020-07-08 00:00:00' AND '2020-07-11 23:59:59' AND pfv.field_key = 'listing_date')
GROUP BY    p.id

Goal

Ultimately, what I would need to be able to do is search on unlimited key/value pairs in this table and return all results grouped by the p.id

Thanks for your help!

Answer 1

This should do the thing.

SELECT      p.name, p.id
FROM        ProjectFieldValue pfv
LEFT JOIN   Project p
    ON      pfv.project_id = p.id
WHERE       (field_key = 'contract_status' AND pfv.text_value = 'Active')
    OR      (field_key = 'contract_client_type' AND pfv.text_value = 'Seller')
    OR      (pfv.field_key = 'listing_date' AND pfv.date_value between '2020-07-08 00:00:00' AND '2020-07-11 23:59:59')
GROUP BY    p.id;

But I have doubt why you are Left joining Project and ProjectFieldValue. A simple Inner Join should solve your purpose. As you are grouping by on p.id. You may encourage a lot of NULLed columns. So I would suggest below.

SELECT      p.name, p.id
FROM        Project p
JOIN        ProjectFieldValue pfv
    ON      p.id = pfv.project_id
WHERE       (field_key = 'contract_status' AND pfv.text_value = 'Active')
    OR      (field_key = 'contract_client_type' AND pfv.text_value = 'Seller')
    OR      (pfv.field_key = 'listing_date' AND pfv.date_value between '2020-07-08 00:00:00' AND '2020-07-11 23:59:59')
GROUP BY    p.id;