Forked from seanbehan/first-and-last-aggregate-functions-psql.sql
Created
November 22, 2016 11:24
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First and last aggregate functions for Postgresql
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-- Create a function that always returns the first non-NULL item | |
CREATE OR REPLACE FUNCTION public.first_agg ( anyelement, anyelement ) | |
RETURNS anyelement LANGUAGE SQL IMMUTABLE STRICT AS $$ | |
SELECT $1; | |
$$; | |
-- And then wrap an aggregate around it | |
CREATE AGGREGATE public.FIRST ( | |
sfunc = public.first_agg, | |
basetype = anyelement, | |
stype = anyelement | |
); | |
-- Create a function that always returns the last non-NULL item | |
CREATE OR REPLACE FUNCTION public.last_agg ( anyelement, anyelement ) | |
RETURNS anyelement LANGUAGE SQL IMMUTABLE STRICT AS $$ | |
SELECT $2; | |
$$; | |
-- And then wrap an aggregate around it | |
CREATE AGGREGATE public.LAST ( | |
sfunc = public.last_agg, | |
basetype = anyelement, | |
stype = anyelement | |
); |
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