Properties2
| Type | Practice |
| Note created | May 6, 2025 |
A correlated subquery is a specific SQL pattern where an inner query references columns from an outer query. This creates a relationship where the subquery must be re-evaluated for each row processed by the outer query.
As per the official BigQuery documentation, A correlated subquery is “a subquery that references a column from outside that subquery”. This referencing of outer columns distinguishes it from regular subqueries and changes how it gets processed.