It's used to perform intermediate operations before the main query runs. Types of Subqueries in MySQL 1. Single-row Subquery 2. Multiple-row Subquery 3. Multiple-column Subquery 4.

The SQL query uses a function in the WHERE clause that returns a varying number of rows for different input values. This causes the query to fail because the WHERE clause expects a single Boolean ...

I occasionally get tripped up writing scalar subqueries that I believe return a single row but since I messed up return multiple rows. Duckdb will then just pick a row at random. PostgreSQL and MySQL ...