Month and year instead of the date variable - postgresql

Question

I work with PostgreSQL and I have three variables in a function and one of them is of type date:
CREATE OR REPLACE FUNCTION public.fn_reporte_venta_mes(
IN p_fech = date,
IN p_client integer,
IN p_comprobante character
The parameter p_fech serves to enter a date from PHP in format '1111-11-11'. Instead, I want to only insert date a month and year format '1111-11'. But I do not know how to change the data type of the p_fech variable since when I put only the day and month in PHP I get compatibility error.
My complete function:
CREATE OR REPLACE FUNCTION public.fn_reporte_venta(
IN p_fech date,
IN p_client integer,
IN p_comprobante character)
RETURNS TABLE(nro integer, fecha date, tipo character varying, cliente text, porc_igv numeric, st numeric, igv numeric, total numeric) AS
$BODY$
begin
return query
select v.numero_venta,
v.fecha_venta,
tc.descripcion,
concat(apellido_paterno, ' ', apellido_materno, ' ', nombres) as client,
v.porcentaje_igv,
v.sub_total,
v.igv,
v.total
from venta v
inner join cliente cl on v.codigo_cliente = cl.codigo_cliente
inner join tipo_comprobante tc on v.codigo_tipo_comprobante = tc.codigo_tipo_comprobante
where v.estado = 'E' and
(
case when p_fech = '11-11-1111' then
1 = 1
else
v.fecha_venta = p_fech
end
)
and
(
case when p_client = 0 then
1 = 1
else
cl.codigo_cliente = p_client
end
) and
(
case when p_comprobante = '00' then
1 = 1
else
tc.codigo_tipo_comprobante = p_comprobante
end
)
order by 2;
end
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;

Answer 1

Use a character type parameter (text or varchar, not character!) and the function to_date() to convert the input to a date.
Your function, simplified and fixed:
CREATE OR REPLACE FUNCTION public.fn_reporte_venta(p_fech text
, p_client integer
, p_comprobante text)
RETURNS TABLE(nro integer, fecha date, tipo varchar, cliente text
, porc_igv numeric, st numeric, igv numeric, total numeric) AS
$func$
DECLARE
v_fech date := to_date(p_fech, 'YYYY-MM-DD'); -- transform to date
BEGIN
RETURN QUERY
SELECT v.numero_venta,
v.fecha_venta,
t.descripcion,
concat_ws(' ', c.apellido_paterno, c.apellido_materno, c.nombres) AS client,
v.porcentaje_igv,
v.sub_total,
v.igv,
v.total
FROM venta v
JOIN cliente c USING (codigo_cliente)
JOIN tipo_comprobante t USING (codigo_tipo_comprobante)
WHERE v.estado = 'E'
AND (v_fech = '1111-11-11' OR v.fecha_venta = v_fech) -- var goes here
AND (p_client = 0 OR c.codigo_cliente = p_client)
AND (p_comprobante = '00' OR t.codigo_tipo_comprobante = p_comprobante)
ORDER BY 2;
END
$func$ LANGUAGE plpgsql STABLE ROWS 1000;
Always use the ISO-8601 format for date literals (YYYY-MM-DD), which is unambiguous with any locale setting. Don't fall for local syntax dialects, they break if a session should run with a different locale.
I am using a date variable in the plpgsql function, which can be assigned at declaration right away.
This expression is very versatile:
to_date(p_fech, 'YYYY-MM-DD');
to_date() allows to omit elements to the right to 1 for missing data. All of these are valid and result in '2016-01-01':
SELECT to_date('2016-01-01', 'YYYY-MM-DD')
, to_date('2016-1-1' , 'YYYY-MM-DD')
, to_date('2016-01' , 'YYYY-MM-DD')
, to_date('2016-' , 'YYYY-MM-DD')
, to_date('2016' , 'YYYY-MM-DD');
So you can pass in full dates or truncated to month or even year. You always specify a single day this way.
Or to always cover a whole month:
...
v_fech date := to_date(p_fech, 'YYYY-MM'); -- no "-DD" truncates to month
...
AND (v_fech = '1111-11-01' -- also truncated to 1st of month!
OR v.fecha_venta >= v_fech
AND v.fecha_venta < v_fech + interval '1 month')
...
Why not data type character? Because that's an outdated, largely useless type, typically a misunderstanding:
Best way to check for "empty or null value"
Any downsides of using data type "text" for storing strings?
Also note how I replaced your verbose CASE statements with simple OR expressions.
And some other minor improvements ...