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+--
+-- Perl Weekly Challenge 260
+-- Task 1
+-- See <https://perlweeklychallenge.org/blog/perl-weekly-challenge-260>
+--
+
+CREATE SCHEMA IF NOT EXISTS pwc260;
+
+CREATE OR REPLACE FUNCTION
+pwc260.task1_plpgsql( nums int[] )
+RETURNS boolean
+AS $CODE$
+
+   WITH numbers AS (
+   	SELECT n
+	FROM unnest( nums ) n
+	)
+   , counting AS (
+	SELECT n, count(*) AS c
+	FROM numbers
+	GROUP BY n
+	)
+   , grouping AS (
+     	SELECT c, count(*) AS g
+	FROM counting
+	GROUP BY c
+	)
+   SELECT NOT EXISTS( SELECT g
+   	      	      FROM grouping
+   		      WHERE g > 1
+		      );
+
+$CODE$
+LANGUAGE sql;