SQL Server stored procedure passing old values not new value - sql-server

Question

This is my table:
search_id search_term clicked count
------------------------------
1 rabbit 0 5
2 airline 1 4
And this is my stored procedure:
alter procedure update_item
(#search_id int,
#search_term varchar(50),
#clicked int)
as
begin
update search_events
set search_term= #search_term,
clicked = #clicked
where search_id = #search_id
end
--exec update_item #search_id=1,#search_term='rabbit',#clicked=0
I created a stored procedure and I pass two parameters.
I want to pass only one of parameter to update the record and second parameter value will be old value.
It is possible that passing the parameter with the old value.
For example:
exec update_item #search_id= 1, #search_term= 'pass here old value that it is rabbit', #clicked = 1
Update only clicked value that it is 1 from 0.

Answer 1

If you only need a single parameter, you can use a simple if statement, and omit the set clause if the value is null
CREATE PROCEDURE update_item (
#search_id INT
,#search_term VARCHAR(50)
,#clicked INT
)
AS
BEGIN
IF (#search_term IS NULL)
UPDATE search_events
SET clicked = #clicked
WHERE search_id = #search_id
ELSE
UPDATE search_events
SET search_term = #search_term
,clicked = #clicked
WHERE search_id = #search_id
END
If you have more parameters that you need to check, then you'd need to build the update statement dynamically. A basic example as follows:
ALTER PROCEDURE update_item (
#search_id INT
,#search_term VARCHAR(50)
,#clicked INT
)
AS
BEGIN
DECLARE #Sql NVARCHAR(4000) = N'UPDATE search_events SET ',
#Params NVARCHAR(300) = N'#search_id INT, #search_term VARCHAR(50), #clicked INT'
IF (#search_term IS NOT NULL)
SET #Sql = #Sql + ' search_term = #search_term,'
SET #Sql = #Sql + ' clicked = #clicked'
SET #Sql = #Sql + ' WHERE search_id = #search_id'
EXEC sp_executesql #Sql, #Params, #search_id=#search_id, #search_term=#search_term, #clicked=#clicked
END