Use If between the where clause - sql

Question

I don't know how exactly I should frame my Question as even I don't know what exactly I have to search. May be this is the best place to put my question. I want to use If condition in where clause this can be done using case but my problem is I don't want to use it after a column name instead I want to avoid entire execution of that column. You can understand it by going through my procedure in the last I have commented, So I want to achieve something like that as I want to write the same procedure again for that condition which i think can be achievable by doing something like that. I searched on internet what I got is to use case in where which doesn't satisfy my purpose. Please look the last lines to understand the problem. Thanx
USE [overseascrm]
GO
/****** Object: StoredProcedure [dbo].[candidatesearch] Script Date: 05-07-2014 00:48:17 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER procedure [dbo].[candidatesearch]
#candidate_id varchar(50),
#firstname varchar(50),
#lastname varchar(50),
#emailid_1 varchar(100),
#mobile_1 varchar(20),
#from varchar(50),
#to varchar(50),
#agentid varchar(50),
#passportno varchar(50),
#profession int,
#isactive bit
as
begin
DECLARE #candidateid_var varchar(50)
DECLARE #firstname_var varchar(50)
DECLARE #lastname_var varchar(50)
DECLARE #emailid1_var varchar(100)
DECLARE #mobile_1_var varchar(20)
DECLARE #agentid_var varchar(50)
IF(#agentid = '')
begin
SET #agentid_var = '%'
END ELSE BEGIN
SET #agentid_var = #agentid
END
IF (#candidate_id = '') BEGIN
SET #candidateid_var = '%'
END ELSE BEGIN
SET #candidateid_var = #candidate_id
END
IF (#firstname = '') BEGIN
SET #firstname_var = '%'
END ELSE BEGIN
SET #firstname_var = #firstname
END
IF (#lastname = '') BEGIN
SET #lastname_var = '%'
END ELSE BEGIN
SET #lastname_var = #lastname
END
IF (#emailid_1 = '') BEGIN
SET #emailid1_var = '%'
END ELSE BEGIN
SET #emailid1_var = #emailid_1
END
IF (#mobile_1 = '') BEGIN
SET #mobile_1_var = '%'
END ELSE BEGIN
SET #mobile_1_var = #mobile_1
END
IF (#from = '') BEGIN
SELECT
*
FROM candidate C
LEFT JOIN candidate_profession_map CM
ON C.candidate_id = CM.candidate_id
LEFT JOIN passport_details PD
ON C.candidate_id = PD.candidate_id
WHERE C.candidate_id LIKE '' + #candidateid_var + '%'
AND firstname LIKE '' + #firstname_var + '%'
AND lastname LIKE '' + #lastname_var + '%'
AND emailid_1 LIKE '' + #emailid1_var + '%'
AND mobile_1 LIKE '' + #mobile_1_var + '%'
AND agent_id LIKE '' + #agentid_var + '%'
AND CM.profession_id = #profession
AND C.isactive = #isactive
AND PD.passport_no = #passportno
END ELSE BEGIN
SELECT
*
FROM candidate C
LEFT JOIN candidate_profession_map CM
ON C.candidate_id = CM.candidate_id
LEFT JOIN passport_details PD
ON C.candidate_id = PD.candidate_id
WHERE C.candidate_id LIKE '' + #candidateid_var + '%'
AND firstname LIKE '' + #firstname_var + '%'
AND lastname LIKE '' + #lastname_var + '%'
AND emailid_1 LIKE '' + #emailid1_var + '%'
AND mobile_1 LIKE '' + #mobile_1_var + '%'
AND agent_id LIKE '' + #agentid_var + '%'
AND C.addedon BETWEEN CONVERT(DATETIME, #from, 103) AND CONVERT(DATETIME, #to, 103)
--IF (#profession <> 0)BEGIN
--AND CM.profession_id = #profession
--END
AND C.isactive = #isactive
OR PD.passport_no = #passportno
END
END

Answer 1

You could use dynamic sql execution where you create your select statement as varchar to your liking, executing it at the end using sp_executesql
http://msdn.microsoft.com/en-us/library/ms188001.aspx

Answer 2

ALTER procedure [dbo].[candidatesearch]
#candidate_id varchar(50),
#firstname varchar(50),
#lastname varchar(50),
#emailid_1 varchar(100),
#mobile_1 varchar(20),
#from varchar(50),
#to varchar(50),
#agentid varchar(50),
#passportno varchar(50),
#profession int,
#isactive bit
AS Begin
SELECT *
FROM candidate C
LEFT JOIN candidate_profession_map CM ON C.candidate_id = CM.candidate_id
LEFT JOIN passport_details PD ON C.candidate_id = PD.candidate_id
WHERE (#candidateid='' or C.candidate_id LIKE #candidateid + '%')
AND (#firstname = '' or firstname LIKE #firstname + '%')
AND (#lastname = '' or lastname LIKE #lastname + '%')
AND (#emailid_1='' or emailid_1 LIKE #emailid1 + '%')
AND (#mobile_1 = '' or mobile_1 LIKE #mobile_1 + '%')
AND (#agentid='' agent_id LIKE #agentid + '%')
AND C.isactive = #isactive
And ((#from=''
AND CM.profession_id = #profession
AND PD.passport_no = #passportno)
or (#from<>''
And C.addedon BETWEEN CONVERT(DATETIME, #from, 103) AND CONVERT(DATETIME, #to, 103)
OR PD.passport_no = #passportno)
End