SQL Stored procedure if (#variable = 0) doesn't work - sql

Question

I've created a Stored procedure with some variables and a nested if statement.
When I call the Stored procedure from my program and check the returned dataset for the returned values, my dataset is empty while there should be records in it. After some testing I noticed when the statement if (#PoolID = 0) is tested and #PoolID is 0, it won't go trough the if statement... So whenever I set the variable poolid to 0 in my code I get the results from the else statement...
Anybody who knows what's going wrong?
Thx
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[Pool_select]
#PartnerCode nvarchar(8),
#GebrID int,
#PoolID int,
#Bevoegdheid int
AS
IF (#PoolID = 0)
BEGIN
IF (#Bevoegdheid < 3)
BEGIN
SELECT
p.*,
pr.poolrecht
FROM racpPool p, racpPoolrecht pr
WHERE
p.poolid = pr.poolid and
p.PartnerCode = #PartnerCode and
pr.poolrecht > 0 and
p.actief = 1 and
pr.GebrID = #GebrID
END
ELSE
BEGIN
SELECT *
FROM racpPool p
WHERE standaardpool = 1
and partnercode = #PartnerCode
END
END
ELSE
BEGIN
IF (#Bevoegdheid < 3)
BEGIN
SELECT
p.*,
pr.poolrecht
FROM racpPool p, racpPoolrecht pr
WHERE
p.poolid = pr.poolid and
p.PartnerCode = #PartnerCode and
pr.poolrecht > 0 and
p.actief = 1 and
pr.GebrID = #GebrID and
p.PoolID = #PoolID
END
ELSE IF (#Bevoegdheid >= 3)
BEGIN
SELECT *
FROM racpPool p
WHERE PoolID = #PoolID
END
END

Answer 1

You could rewrite it as one single select of 4-part UNION ALL.
I also notice that your conditions are not comprehensive, not sure if that is intentional.
In the 2nd branch of #PoolID = 0 , the tests are specifically #Bevoegdheid < 3 and #Bevoegdheid >= 3 (instead of ELSE ) which will do nothing if #Bevoegdheid IS NULL
The optimizer will only run the branch that fits the criteria marked with <<<
ALTER PROCEDURE [dbo].[Pool_select]
#PartnerCode nvarchar(8),
#GebrID int,
#PoolID int,
#Bevoegdheid int
-- WITH RECOMPILE -- << may need this
AS
SELECT
p.*,
pr.poolrecht
FROM racpPool p, racpPoolrecht pr
WHERE
p.poolid = pr.poolid and
p.PartnerCode = #PartnerCode and
pr.poolrecht > 0 and
p.actief = 1 and
pr.GebrID = #GebrID
AND #PoolID = 0 and #Bevoegdheid < 3 --- <<<
UNION ALL
SELECT *, NULL
FROM racpPool p
WHERE standaardpool = 1
and partnercode = #PartnerCode
AND #PoolID = 0 and IsNull(#Bevoegdheid,4) >= 3 --- <<<
UNION ALL
SELECT
p.*,
pr.poolrecht
FROM racpPool p, racpPoolrecht pr
WHERE
p.poolid = pr.poolid and
p.PartnerCode = #PartnerCode and
pr.poolrecht > 0 and
p.actief = 1 and
pr.GebrID = #GebrID and
p.PoolID = #PoolID
AND Isnull(#PoolID,-1) <> 0 AND #Bevoegdheid < 3 --- <<<
UNION ALL
SELECT *, NULL
FROM racpPool p
WHERE PoolID = #PoolID
AND Isnull(#PoolID,-1) <> 0 AND #Bevoegdheid >= 3 --- <<<