case stement when null

hi all,

Well i rethink my design 'cause the other was too slow. but all solutions
involves new problems... now my problem is with a function of this type:

CREATE OR REPLACE FUNCTION "public"."rec_f_consultarplanificacionrubros"
(smallint, smallint, char(9), smallint, smallint, smallint, char(2)) RETURNS
SETOF "public"."rec_td_rubrosplanificados" AS '
select rub_codigo, cpa_valor, cpa_fechavencimiento
from rec_m_cuadropagosciclo
where ent_codigo = $1
and sec_codigo = $2
and ani_codigo = $3
and case $4
when null then cic_codigo IN (select cic_codigo from
aca_m_cicloaniolectivo
where ent_codigo =
$1
and sec_codigo =
$2
and ani_codigo =
$3)
else cic_codigo = $4
end
' LANGUAGE 'sql'

but when $4 is null the function executes the else part and what i want to
do is to execute the when null. Can you help me???

Thanx in advance,

Jaime Casanova

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