Create dynamic SQL query for search - sql

Question

I need to create a SQL query to return data from a table and use condition in where but I where not have not have fixed condition, may be condition have 2 or 3 parameters, I want to avoid the IF #PARAMETER >0. I want to use a better and cleaner way to solve it.
This is my query :
CREATE PROCEDURE GetAllUsers(#p1 , #p2 , #p3 , #p4)
AS
BEGIN
SELECT
firstName,
lastName,
email
FROM
[USERS]
WHERE
id = #p4 AND firstName = #p2
END
How can I solve this issue?

Answer 1

You can use COALESCE to make a parameter equal to the column it is being compared against when it is NULL, so that the test passes if you pass NULL for the parameter value. For example:
SELECT
firstName,
lastName,
email
FROM [USERS]
WHERE id=COALESCE(#p4,id) AND firstName=COALESCE(#p2,firstName)
So when calling your procedure and wanting to fetch all John regardless of id you would use
GetAllUsers('somevalue' , 'John' , 'someothervalue' , NULL)

Answer 2

You can pass NULL to parameter which are not required and write your query like following.
SELECT firstName, lastName, email
FROM [USERS]
WHERE (
#p4 IS NULL
OR id = #p4
)
AND (
#p2 IS NULL
OR firstName = #p2
)
Similarly you can build your query by adding other parameter.
NOTE: Syntax of your CREATE PROCEDURE is not correct, you need to mention the datatype of the parameters.
You can also use the default values to your parameters. Your final SP should look like following
CREATE PROCEDURE GetAllUsers (
#p1 INT = NULL
,#p2 VARCHAR(100) = NULL
,#p3 VARCHAR(100) = NULL
,#p4 VARCHAR(100) = NULL
)
AS
BEGIN
SELECT firstName
,lastName
,email
FROM [USERS]
WHERE (
#p4 IS NULL
OR id = #p4
)
AND (
#p2 IS NULL
OR firstName = #p2
)
--Add remaining conditions
END