Built-in functions and operatorsBuilt-in functions and operatorsThis chapter provides an overview of built-in functions and operators. Scalar functions String functionsDate and time functionsGeo functionsMathematical functionsRegular expression functionsArray functionsConditional functions and expressionsSystem information functionsSpecial functions Aggregation Aggregate expressionsAggregate functionsLimitations Arithmetic operatorsTable functions Scalar functionsempty_row( )unnest( array [ array , ] )pg_catalog.generate_series(start, stop, [step])pg_catalog.generate_subscripts(array, dim, [reverse])regexp_matches(source, pattern [, flags])pg_catalog.pg_get_keywords()information_schema._pg_expandarray(array) Comparison operators Basic operatorsWHERE clause operators Array comparisons IN (value [, ...])ANY/SOME (array expression)ALL (array_expression) Subquery expressions IN (subquery)ANY/SOME (subquery)ALL (subquery) Window functions Window function callWindow definitionGeneral-purpose window functionsAggregate window functions