MySQL 8.0

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CREATE TABLE posts (id INT, title VARCHAR(50));
INSERT INTO posts (id, title) VALUES (1, 'Post A'), (2, 'Post B'), (3, 'Post C');

CREATE TABLE tags (id INT, name VARCHAR(50));
INSERT INTO tags (id, name) VALUES (1, 'Tag 1'), (2, 'Tag 2'), (3, 'Tag 3');

CREATE TABLE tags_posts  (post INT, tag INT);
INSERT tags_posts  (post, tag) VALUES (1, 1), (1, 2), (2, 3);

CREATE TABLE blocked_tags (user VARCHAR(50), tag INT);
INSERT blocked_tags (user, tag) VALUES ('user1', 1), ('user1', 2), ('user2', 3);

Records: 3  Duplicates: 0  Warnings: 0



Records: 3  Duplicates: 0  Warnings: 0



Records: 3  Duplicates: 0  Warnings: 0



Records: 3  Duplicates: 0  Warnings: 0


SELECT	p.id, 
		p.title,
		GROUP_CONCAT(t.name) AS tags
FROM	posts AS p
		LEFT JOIN tags_posts AS tp
			ON tp.post = p.id
		LEFT JOIN tags AS t
			ON t.id = tp.tag
		LEFT JOIN blocked_tags AS bt
			ON bt.tag = tp.tag
			AND bt.user = 'user1'
GROUP BY p.id, p.title
HAVING COUNT(bt.tag) = 0 /*No blocked tags*/


id
title
tags


2
Post B
Tag 3

3
Post C
null


SELECT	p.id, 
		p.title,
		GROUP_CONCAT(t.name) AS tags
FROM	posts AS p
		LEFT JOIN tags_posts AS tp
			ON tp.post = p.id
		LEFT JOIN tags AS t
			ON t.id = tp.tag
		LEFT JOIN blocked_tags AS bt
			ON bt.tag = tp.tag
			AND bt.user = 'user2'
GROUP BY p.id, p.title
HAVING COUNT(bt.tag) = 0 /*No blocked tags*/


id
title
tags


1
Post A
Tag 2,Tag 1

3
Post C
null


SELECT	p.id, 
		p.title,
		GROUP_CONCAT(t.name) AS tags
FROM	posts AS p
		LEFT JOIN tags_posts AS tp
			ON tp.post = p.id
		LEFT JOIN tags AS t
			ON t.id = tp.tag
		LEFT JOIN blocked_tags AS bt
			ON bt.tag = tp.tag
			AND bt.user = 'user3'
GROUP BY p.id, p.title
HAVING COUNT(bt.tag) = 0 /*No blocked tags*/


id
title
tags


1
Post A
Tag 2,Tag 1

2
Post B
Tag 3

3
Post C
null