Filter SQL datatable according to different parameters, without a WHERE clause - sql-server

Question

I'm building an application that needs to allow the user to filter a data table according to different filters. So, the user will have three different filter posibilites but he might use only one, or two or the three of them at the same tame.
So, let's say I have the following columns on the table:
ID (int) PK
Sede (int)
Programa (int)
Estado (int)
All of those columns will store numbers, integers. The "ID" column is the primary key, "Sede" stores 1 or 2, "Programa" is any number between 1 and 15, and "Estado" will store numbers between 1 and 13.
The user may filter the data stored in the table using any of those filters (Sede, Programa or Estado). But the might, as well, use two filters, or the three of them at the same time.
The idea is that this application works like the data filters on Excel. I created a simulated table on excel to show what I want to achieve:
This first image shows the whole table, without applying any filter.
Here, the user selected a filter for "Sede" and "Programa" but leaved the "Estado" filter empty. So the query returns the values that are equal to the filter, but leaves the "Estado" filter open, and brings all the records, filering only by "Sede" (1) and "Programa" (6).
In this image, the user only selected the "Estado" filter (5), so it brings all the records that match this criteria, it doesn't matter if "Sede" or "Programa" are empty.
If I use a SELECT clasuse with a WHERE on it, it will work, but only if the three filters have a value:
DECLARE #sede int
DECLARE #programa int
DECLARE #estado int
SET #sede = '1'
SET #programa = '5'
SET #estado = '12'
SELECT * FROM [dbo].[Inscripciones]
WHERE
([dbo].[Inscripciones].[Sede] = #sede)
AND
([dbo].[Inscripciones].[Programa] = #programa)
AND
([dbo].[Inscripciones].[Estado] = #estado)
I also tryed changing the "AND" for a "OR", but I can't get the desired result.
Any help will be highly appreciated!! Thanks!

Answer 1

common problem: try using coalesce on the variable and for the 2nd value use the field name you're comparing to. Be careful though; Ensure it's NULL and not empty string being passed!
What this does is take the first non-null value of the variable passed in or the value you're comparing to.. Thus if the value passed in is null the comparison will always return true.
WHERE
[dbo].[Inscripciones].[Sede] = coalesce(#sede, [dbo].[Inscripciones].[Sede])
AND
[dbo].[Inscripciones].[Programa] = coalesce(#programa, [dbo].[Inscripciones].[Programa])
AND
[dbo].[Inscripciones].[Estado] = coalesce(#estado, [dbo].[Inscripciones].[Estado])
If sede is null and programa and estado are populated the compare would look like...
?=? (or 1=1)
?=programa variable passed in
?=Estado variable passed in
Boa Sorte!

Answer 2

Thank you all for your anwers. After reading the article posted in the comments by #SeanLange I was finally able to achieve what was needed. Using a CASE clause in the WHERE statement solves the deal. Here's the code:
SELECT
*
FROM [dbo].[Inscripciones]
WHERE
([dbo].[Inscripciones].[Sede] = (CASE WHEN #sede = '' THEN [dbo].[Inscripciones].[Sede] ELSE #sede END))
AND
([dbo].[Inscripciones].[Programa] = (CASE WHEN #programa = '' THEN [dbo].[Inscripciones].[Programa] ELSE #programa END))
AND
([dbo].[Inscripciones].[Estado] = (CASE WHEN #estado = '' THEN [dbo].[Inscripciones].[Estado] ELSE #estado END))
AND
([dbo].[Inscripciones].[TipoIngreso] = (CASE WHEN #tipoingreso = '' THEN [dbo].[Inscripciones].[TipoIngreso] ELSE #tipoingreso END))
Thanks again!!