Category: SQL

Combine result sets and keep duplicates with UNION ALL.

Nest queries inside SELECT/WHERE/FROM for multi-step logic.

Combine related tables with JOIN operations.

Return matching rows from both tables.

Write conditional logic in queries with CASE.

Use MySQL IF / IFNULL helpers for simple conditionals and null defaults.

Return the first non-null expression with COALESCE.

Filter groups after aggregation with HAVING.

Rename columns/tables in queries with AS aliases.

Transform text with CONCAT, SUBSTRING, LENGTH, REPLACE, TRIM, and more.