Complex NOT EXISTS MySQL query - To ignore multiple matches - php

Question

Below is a snippet from a large query I am running which performs a search on a table full of products. This snippet excludes certain products from appearing in results unless it's overridden (a tag ID is specified eg.search criteria is made).
Here's a couple of tag ID's and their names:
Tag ID 576 = 'Santa'
Tag ID 123 = 'Christmas'
So basically the below will exclude all products in the 'tags_gifts_occasion_specific' table unless they have a tag ID of 576 ('Santa').
AND NOT EXISTS (
SELECT *
FROM tags_gifts_occasion_specific
WHERE tags_gifts_occasion_specific.tag_id != '576'
GROUP BY tags_gifts_occasion_specific.gift_id
)
Simple right....
But the problem is if the same product is in this table but has a different tag ID applied to it... eg it also is in there for the tag 'Christmas'.
Of course it would be easy to just add 'AND tags_gifts_occasion_specific.tag_id != '123', however the query doesn't know what additional ID's it shouldn't look for - only the one that has been searched for.
I have been playing around with something like the following but unsuccessfuly. I thought I could count the number of occurences of gift_id and if it was already found then ignore any further - any fresh input would be greatly appreciated.
AND NOT EXISTS (
SELECT * , COUNT( * ) AS no_gifts
FROM tags_gifts_occasion_specific
WHERE tags_gifts_occasion_specific.tag_id != '576'
HAVING no_gifts < 1
GROUP BY tags_gifts_occasion_specific.gift_id
)
** FURTHER DETAIL REGARDING ORDER BY BUG **
So the order by bug is as follows. If someone searches for 'wedding' & 'bridemaid' gifts, wedding or bridemaid gifts should be returned with matches for both showed first, then the rest based on popularity. This works for all searches that do not have gifts in the 'tags_gifts_occasion_specific' table.
SELECT gifts.affiliate_id, gifts.gift_id, gifts.gift_title, gifts.gift_price, gifts.gift_image, gifts.gift_slug
FROM gifts
LEFT JOIN tags_gifts_occasion_specific AS os ON gifts.gift_id = os.gift_id
LEFT JOIN tags_gifts ON tags_gifts.gift_id = gifts.gift_id
LEFT JOIN tags ON tags.id = tags_gifts.tag_id
LEFT JOIN popularity ON popularity.gift_id = gifts.gift_id AND popularity.tag_id = tags.id
WHERE published = '1' AND in_seekgifts = '1'
AND ( (tags_gifts.tag_id = '576' OR tags_gifts.tag_id = '340') )
AND NOT EXISTS (
SELECT * FROM tags_gifts_occasion_specific x WHERE x.gift_id = gifts.gift_id
AND NOT EXISTS(
SELECT * FROM tags_gifts_occasion_specific x1 WHERE x.gift_id = x1.gift_id AND ( tag_id IN (576) OR tag_id in (340) ) )
)
GROUP BY gifts.gift_id
ORDER BY COUNT(*) DESC , popularity.popularity DESC, gifts.gift_popularity DESC, gifts.gift_id DESC
Live example of results:
http://www.seekgifts.co.uk/wedding_bridesmaid/
What I think is happening is that it can see the products in the top are in the tags_gifts_occasion_specific table for multiple tags and is therefore ordering by the number of times it is found in this table. Not sure how to get round this one?

Answer 1

As far as I understand, there is a table with products, and there is a table with tags for each product.
And the query is expected to skip products that have some tag, and include products that don't have these tags.
For example:
Products
| PRODUCT_ID | PRODUCT_NAME |
|------------|--------------|
| 1 | Product 1 |
| 2 | Product 2 |
| 3 | Product 3 |
| 4 | Product 4 |
| 5 | Product 5 |
Tags
| PRODUCT_ID | TAG |
|------------|--------------|
| 1 | Santa |
| 1 | Christmas |
| 2 | Christmas |
| 3 | Santa |
| 4 | Christmas |
| 4 | Exclude |
| 4 | Dont exclude |
| 5 | Christmas |
| 5 | Dont exclude |
And we want to skip rpoducts, that have tags Santa and Exclude.
In the above example, we want to skip products 1, 3 and 4, and include products 2, 5.
We can do it using the following correlated subquery
SELECT * from products p
WHERE
NOT EXISTS(
SELECT 1 FROM tags t
WHERE t.product_id = p.product_id
AND t.tag IN ( 'Santa', 'Exclude' )
)
;
| PRODUCT_ID | PRODUCT_NAME |
|------------|--------------|
| 2 | Product 2 |
| 5 | Product 5 |
Here is a link to a working demo: http://sqlfiddle.com/#!2/d880d/4
EDIT
An example for your schema
Gifts
select * from `gifts`;
| GIFT_ID | GIFT_TITLE |
|---------|------------------------|
| 1 | Red Christmas stocking |
| 2 | Santa Clause Socks |
| 3 | 40th Birthday Mug |
| 4 | Red Bowl |
tags_gifts_occasion_specific
select * from `tags_gifts_occasion_specific`
order by gift_id, tag_id;
| TAG_ID | GIFT_ID |
|--------|---------|
| 3 | 2 |
| 4 | 2 |
| 4 | 3 |
| 3 | 4 |
This query gets all entries from tags_gifts_occasion_specific, except these ones for which exists a tag_id = 3
select * from `tags_gifts_occasion_specific` x
where not exists(
select 1 from `tags_gifts_occasion_specific` x1
where x.gift_id = x1.gift_id
and tag_id in ( 3 )
);
| TAG_ID | GIFT_ID |
|--------|---------|
| 4 | 3 |
Now we use the above query to exclude some records from gifts table:
select * from `gifts` g
where not exists(
select 1 from `tags_gifts_occasion_specific` x
where g.gift_id = x.gift_id
and not exists(
select 1 from `tags_gifts_occasion_specific` x1
where x.gift_id = x1.gift_id
and tag_id in ( 3 )
)
);
| GIFT_ID | GIFT_TITLE |
|---------|------------------------|
| 1 | Red Christmas stocking |
| 2 | Santa Clause Socks |
| 4 | Red Bowl |
| 5 | Red 40th Birthday Vase |
Here is a link to a demo: http://sqlfiddle.com/#!2/558422/5