Do CTEs always improve performance? Explain how engines may inline or materialize them and how you decide.

Problem Statement

Explanation

A CTE is a query organization tool. Some engines inline it like a view, so it behaves like a subquery. Others may materialize it into a temporary result. The choice can change the plan and memory use. Decide by measuring with an execution plan. If reuse or expensive re-computation is the issue, a temp table with an index can win. If clarity is the goal and the step is cheap, a CTE is ideal.

Code Solution

SolutionRead Only

WITH t AS (SELECT * FROM big WHERE flag=1)
SELECT COUNT(*) FROM t;

Practice Sets

This question appears in the following practice sets:

Subqueries & CTEs (incl. Recursive)

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Do CTEs always improve performance? Explain how engines may inline or materialize them and how you decide.

Problem Statement

Explanation

Code Solution

Practice Sets

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Master Interviews Anywhere, Anytime

Do CTEs always improve performance? Explain how engines may inline or materialize them and how you decide.

Problem Statement

Explanation

Code Solution

Practice Sets

Related Questions

Which SQL statement retrieves all columns and rows from a table named employees?

Which clause filters rows before aggregation and affects which rows are grouped?

What is the default sort order when ORDER BY is used without ASC or DESC?

Which construct is commonly used to paginate results in SQL engines like Postgres and MySQL?

Which predicate correctly checks for missing values in standard SQL?

More from SQL & Databases

Master Interviews
Anywhere, Anytime