Error in sql server Query

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[advSearch]
(
	@createdBy varchar(50) ,
	@subject varchar(200),
	@details nvarchar(MAX),
	@againstCompany varchar(100),
	@headOfficeAdd varchar(200),
	@deilveryOfficeAdd varchar(250)
	
)
AS

BEGIN
DECLARE @_s varchar(MAX)
DECLARE @_id int

select TOP 1 @_id = _id from tbl_User where _userName like '%'+ @createdBy+'%';

SELECT @_id;
SET NOCOUNT ON;

SET @_s='select * from tbl_Alert where isActive=1';

if @createdBy<>''
	BEGIN 

		SET @_s=@_s+' and createdBy ='+@_id;
	END 

if @subject<>''
	BEGIN 

		SET @_s=@_s+' and subject like ''%'+ @subject+'%''';
	END 

if @details<>''
	BEGIN 

		SET @_s=@_s+' and details like ''%'+ @details+'%''';
	END

if @againstCompany<>''
	BEGIN 

		SET @_s=@_s+' and againstCompany like ''%'+ @againstCompany+'%''';
	END

if @headOfficeAdd<>''
	BEGIN 

		SET @_s=@_s+' and headOfficeAdd like ''%'+ @headOfficeAdd+'%''';
	END

if @deilveryOfficeAdd<>''
	BEGIN 

		SET @_s=@_s+' and deilveryOfficeAdd like ''%'+ @deilveryOfficeAdd+'%''';
	END

exec(@_s)

END


SET ANSI_NULLS ON
SET QUOTED_IDENTIFIER ON