Part 59: String Aggregation: STRING_AGG & GROUP_CONCAT

Aggregate functions can also concatenate text strings across rows.

1. PostgreSQL: STRING_AGG()

SELECT 
  post_id,
  STRING_AGG(tag_name, ', ' ORDER BY tag_name) AS tags
FROM post_tags
GROUP BY post_id;

2. MySQL: GROUP_CONCAT()

SELECT 
  post_id,
  GROUP_CONCAT(tag_name ORDER BY tag_name SEPARATOR ', ') AS tags
FROM post_tags
GROUP BY post_id;

Key Takeaways

• Concatenate multiple child records into a comma-delimited string without N+1 queries.

In Part 60, we conclude Module 6 with a Real-World Sales Analytics Dashboard Query Project!