Dynamic Where Condition Based on Parameter Value in sql - sql-server

Question

I am doing a search Criteria Form in that i have various types of search options,Instead of doing a If condition in code based on the control select, we can check by the parameter values and update the where condition
Declare #Amount varchar(Max);
SET #Amount= 'and Amount=500';
Select Processor, [Stmt Date], Description, Amount, [Allocation Date],
Entity, URN, [Customer Acc], [Invoice Number],Lamount, DumpEntity as [Received Entity]
from tbl_Employee_Salary
WHERE 1=1 +CONVERT(int,CASE when #Amount IS NOT null then #Amount Else ' ' END)
Conversion failed when converting the varchar value 'and Amount=500'
to data type int.

Answer 1

Warning: This is completely untested.
I hate these types of queries, but what you are after is something like this. I'm not going to explain it, sorry, but it's up to you to understand the below and support it yourself. This is known as a catch-all query or a kitchen sink query.
--All below datatypes are ASSUMED
--Declare a variable for every column (you won't need all of these if they aren't going to all be used)
DECLARE #Processor varchar(50),
#StmtDate date,
#Description varchar(100),
#Amount int,
#AllocationDate date,
#Entity int,
#URN int,
#CustomerAcc int,
#InvoiceNumber int,
#Lamount decimal(10,2),
#DumpEntity varbinary(8);
--Set your values here (I assume this will actually be an SP or something)
SET #Amount = 500;
--Create the initial SQL statement
DECLARE #SQL nvarchar(MAX);
SET #SQL = N'SELECT Processor,' + NCHAR(13) + NCHAR(10) +
N' [Stmt Date],' + NCHAR(13) + NCHAR(10) +
N' Description,' + NCHAR(13) + NCHAR(10) +
N' Amount,' + NCHAR(13) + NCHAR(10) +
N' [Allocation Date],' + NCHAR(13) + NCHAR(10) +
N' Entity,' + NCHAR(13) + NCHAR(10) +
N' URN,' + NCHAR(13) + NCHAR(10) +
N' [Customer Acc],' + NCHAR(13) + NCHAR(10) +
N' [Invoice Number],' + NCHAR(13) + NCHAR(10) +
N' Lamount,' + NCHAR(13) + NCHAR(10) +
N' DumpEntity AS [Received Entity]' + NCHAR(13) + NCHAR(10) +
N'FROM tbl_Employee_Salary'
--Now you need to start creating the WHERE
DECLARE #Where nvarchar(MAX);
SET #Where = N'WHERE ' +
NULLIF(STUFF(CASE WHEN #Processor IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND Processor = #Processor' ELSE N'' END +
CASE WHEN #StmtDate IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND [Stmt Date] = #StmtDate' ELSE N'' END +
CASE WHEN #Description IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND [Description] = #Description' ELSE N'' END +
CASE WHEN #Amount IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND Amount = #Amount' ELSE N'' END +
CASE WHEN #AllocationDate IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND [Allocation Date] = #AllocationDate' ELSE N'' END +
CASE WHEN #Entity IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND Entity = #Entity' ELSE N'' END +
CASE WHEN #URN IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND URN = #URN' ELSE N'' END +
CASE WHEN #CustomerAcc IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND [Customer Acc] = #CustomerAcc' ELSE N'' END +
CASE WHEN #InvoiceNumber IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND [Invoice Number] = #InvoiceNumber' ELSE N'' END +
CASE WHEN #Lamount IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND Lamount = #Lamountcessor' ELSE N'' END +
CASE WHEN #DumpEntity IS NOT NULL THEN NCHAR(13) + NCHAR(10) + N' AND DumpEntity = #DumpEntity' ELSE N'' END,1,8,N''),N'');
--Now add the 2 values together
SET #SQL = #SQL + ISNULL(#Where,N'') + N';';
--Create the parameter string
DECLARE #Params nvarchar(MAX);
--All following datatypes are ASSUMED
SET #Params = N'#Processor varchar(50),#StmtDate date,#Description varchar(100),#Amount int,#AllocationDate date, #Entity int,#URN int,#CustomerAcc int,#InvoiceNumber int,#Lamount decimal(10,2),#DumpEntity varbinary(8)'
PRINT #SQL; --Your debugging best friend
--And execute the dynamic SQL
EXEC sp_executesql #SQL, #Params, #Processor, #StmtDate, #Description ,#Amount, #AllocationDate ,#Entity, #URN , #CustomerAcc, #InvoiceNumber, #Lamount, #DumpEntity;
GO
Good luck!