How to merge multiple MySQL query results into a single field?

Other Questions MySQL
1

I’m working with MySQL and need help combining data from multiple rows into one result. Here’s what I’m currently getting:

SELECT interests FROM user_interests WHERE user_id = 10;

Current Result:

reading
swimming
gaming

What I want instead:

reading, swimming, gaming

I’m dealing with complex joins across several tables and ending up with way more rows than necessary. I tried looking into CONCAT and CONCAT_WS functions but they don’t seem to work with multiple query results. Is there a way to combine these rows into a single comma-separated value? Any suggestions would be really helpful!

2

GROUP_CONCAT tanks with large datasets. Hit this hard on a production system - concatenating thousands of interests per user caused timeouts. Switched to application-level concatenation for heavy workloads instead. Just pull the rows normally and join them in your backend code. MySQL holds all matching rows in memory for GROUP_CONCAT, which gets expensive fast. Your smaller dataset should be fine, but watch execution times if this query grows. One more thing - check your collation settings with special characters. GROUP_CONCAT follows the column’s collation and can mess up sorting with mixed case or unicode data.

3

had this exact issue yesterday! GROUP_CONCAT works great but you’ll get duplicates if your joins pull the same values multiple times. just add DISTINCT like GROUP_CONCAT(DISTINCT interests) and you’re golden. saved me a huge headache.

4

Use GROUP_CONCAT - it’s built exactly for this. Concatenates values from multiple rows into one string:

SELECT GROUP_CONCAT(interests) FROM user_interests WHERE user_id = 10;

It defaults to comma separation, which works for you. Want something else? Try GROUP_CONCAT(interests SEPARATOR '; ').

Heads up: there’s a 1024 character limit by default. If you’re dealing with tons of data, bump up the group_concat_max_len setting. I’ve used this tons of times for flattening data in reports - works great.

5

Yeah, duplicate rows from complex joins are a pain. Besides GROUP_CONCAT, try using subqueries for cleaner aggregation. Something like SELECT u.username, (SELECT GROUP_CONCAT(DISTINCT i.interests) FROM user_interests i WHERE i.user_id = u.id) as combined_interests FROM users u keeps everything organized when you’re pulling from multiple tables. This stops the row explosion you get with joins and gives you precise control over what gets concatenated. I use this pattern all the time for multiple many-to-one relationships where regular joins would create a cartesian product nightmare.

6

Yeah GROUP_CONCAT works but gets messy with multiple tables and complex transformations. Been there too many times.

Automating these database operations completely changed everything for me. Instead of fighting SQL limitations, I built workflows that handle data merging automatically.

You could create a flow that pulls user interests, combines them how you want, and pushes results wherever needed. No character limits, no SQL headaches, plus you can filter duplicates or sort alphabetically.

Schedule it to run periodically or trigger on database changes. Way more flexible than pure SQL, especially as your data gets complex.

I’ve automated similar tasks that used to take hours of manual SQL work. Now they run in the background and handle edge cases that’d break normal queries.

Check out Latenode: https://latenode.com