Can I attach multiple tags to a post in a single database query

- A table for the posts (or items).
- A table for the tags.
- A join/linking table that associates posts with tags, where each row represents one tag attached to one post.

To attach multiple tags to a single post in one query, you would typically perform a single bulk insert into the join table with multiple rows - one for each tag-post pair. For example, if your join table is named `post_tags` with columns `post_id` and `tag_id`, you can insert multiple rows in one SQL statement like:

sql
INSERT INTO post_tags (post_id, tag_id) VALUES
  (123, 1),
  (123, 2),
  (123, 3);

This single query attaches three tags (with IDs 1, 2, and 3) to the post with ID 123.

This approach is efficient and scalable, especially compared to storing tags as a comma-separated string in one column, which is generally discouraged because it complicates querying and indexing[2][3][6].

If you want to query posts that have multiple specific tags, you can use SQL with `GROUP BY` and `HAVING` clauses to find posts that have all the desired tags, for example:

sql
SELECT post_id
FROM post_tags
WHERE tag_id IN (1, 2, 3)
GROUP BY post_id
HAVING COUNT(DISTINCT tag_id) = 3;

This query returns posts tagged with all three tags (IDs 1, 2, and 3)[1][5].

In summary:

- Use a many-to-many schema with a linking table to associate posts and tags.
- Attach multiple tags to a post in a single query by inserting multiple rows into the linking table at once.
- Avoid storing multiple tags as delimited strings in one column due to performance and querying issues.
- Use SQL aggregation (`GROUP BY` and `HAVING`) to query posts by multiple tags efficiently.

This method is widely accepted as the proper way to handle multiple tags per post in relational databases[2][3][6].

Citations:
[1] https://stackoverflow.com/questions/38954934/how-to-query-data-based-on-multiple-tags-in-sql
[2] https://www.reddit.com/r/SQL/comments/xuq1lt/how_to_handle_multiple_tags_for_things_like_posts/
[3] https://softwareengineering.stackexchange.com/questions/117886/how-to-design-a-database-wherein-multiple-tagsstring-are-to-be-associated-with
[4] https://forum.inductiveautomation.com/t/retrieving-multiple-db-tags-from-one-sql-query-execution/4021
[5] https://dba.stackexchange.com/questions/226670/select-items-that-has-one-or-more-specific-tags
[6] https://dba.stackexchange.com/questions/176231/storing-multiple-tags-on-analytics-database
[7] https://community.sisense.com/t5/knowledge-base/filtering-on-multiple-tags-in-a-single-row/ta-p/8646
[8] https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-tagging.html