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Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
SQL allows to perform set operations as understood in standard set theory on result sets. These operations include unions, intersections, subtractions. For two subselects to be combinable by such a set operator, each subselect must return a table expression of the same degree and type.
All of these set operations come with 2 flavours:
DISTINCT(the default): Removing duplicates after applying the set operation
ALL: Retaining duplicates after applying the set operation