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Compound SELECT

Result of SELECT statement can be combined with other select statements using one of following operator.

  1. UNION - take a union of result of two queries such that there is no duplicate results.
  2. UNION ALL - take a union of results of two queries.
  3. INTERSECT - take only rows that are common in both queries.
  4. EXCEPT - take rows from first query that are not present in second query.

Simple union with no duplicate rows

SELECT 1 a ,2 b UNION SELECT 1 a, 2 b /* a | b ------ 1 | 2 */

Simple union with duplicate rows

SELECT 1 a ,2 b UNION ALL SELECT 1 a, 2 b /* a | b ------ 1 | 2 1 | 2 */

Simple intersect return only common results

SELECT 1 a ,2 b INTERSECT SELECT 1 a, 2 b /* a | b ------ 1 | 2 */

Except return exclude result from first query by second.

SELECT 1 a ,2 b EXCEPT SELECT 1 a, 2 b /* a | b ------ */

ECSql Syntax

Last Updated: 29 April, 2025