CTE in SQL: Usage Guide

1 year ago
Sophia Anderson
1 minute

CTE, or Common Table Expressions, is a method in SQL used to create temporary result sets. With CTE, users can define a temporary result set within an SQL query and then join this result set with other parts of the query.

The usage instructions for CTE are as follows:

  1. Define a Common Table Expression (CTE) using the WITH keyword, the syntax is as follows:
WITH cte_name AS (
    SELECT column1, column2
    FROM table_name
    WHERE condition
)
  1. Define the columns and rows needed to be returned in a Common Table Expression (CTE) using a SELECT statement. Operations like JOIN, GROUP BY, ORDER BY can be performed within the CTE.
  2. In the main query, you can use a pre-defined CTE by referencing its name in the query, the syntax is as follows:
SELECT *
FROM cte_name
WHERE condition

Through CTE, users can more clearly organize complex SQL queries, improving the readability and maintainability of SQL queries.

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