Built-in functions and operatorsBuilt-in functions and operatorsThis chapter provides an overview of built-in functions and operators. Table of contents 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