SQL partial update of columns based on case statement? - sql

Question

Recently I have had to do a few variable updates to a table, and although I am aware of the MERGE statement (although need to catch up on all of that!), I also performed the following statement to optional update a table and wish to check if this is "a good idea" or has some hidden consequences that I not aware of.
So in my case, I pass a primary key to a table, however depending on if parameters passed are null or not, I update the column.. obviously if you had to ensure a forceful update (of a status etc.) then you would just update the column.. this is to save having multiple "IF / THEN" type structures..
create procedure sp_myprocedure
as
#id bigint,
#field1 int = null,
#field2 varchar(255) = null,
#field3 char(1) = null
begin
update my_table
set
field1 = case when #field1 is not null then #field1 else field1 end,
field2 = case when #field2 is not null then #field2 else field2 end,
field3 = case when #field3 is not null then #field3 else field3 end,
where
id = #id
end
Just after some thoughts of the above or is it best to pursue the MERGE statement for scenarios like the above?
Many thanks in advance,

Answer 1

This is fine although it can be written in a cleaner way.
update my_table
set
field1 = coalesce (#field1,field1)
,field2 = coalesce (#field2,field2)
,field3 = coalesce (#field3,field3)
where
id = #id and coalesce(#field1,#field2,#field3) is not null
You can also move the coalesce(#field1,#field2,#field3) is not null to a wrapper block
if coalesce(#field1,#field2,#field3) is not null
begin
update my_table
set
field1 = coalesce (#field1,field1)
,field2 = coalesce (#field2,field2)
,field3 = coalesce (#field3,field3)
where
id = #id
end
MERGE statement is not relevant here.
With MERGE the decision is if to INSERT, UPDATE or DELETE a record base on the non-existent/existent of a record with the same merge keys in the source/target table.
In your case it is always UPDATE.

Answer 2

create procedure sp_myprocedure
#id bigint,
#field1 int = null,
#field2 varchar(255) = null,
#field3 char(1) = null
as
begin
IF coalesce(#field1,#field2,#field3) is not null
update dbo.my_table
set
field1 = coalesce (#field1,field1),
field2 = coalesce (#field2,field2),
field3 = coalesce (#field3,field3)
where id = #id
END

Answer 3

Responding to the answer by #Dudu Markovitz:
MERGE statement is not relevant here.
I disagree , I think MERGE is entirely relevant here.
The idea is to create a source table expression using the parameter values with which to update the target table:
MERGE my_table T
USING ( VALUES ( #id, #field1, #field2, #field3 ) )
AS S ( id, field1, field2, field3 )
ON T.id = S.id
WHEN MATCHED THEN
UPDATE
SET field1 = COALESCE( S.field1, T.field1 ),
field2 = COALESCE( S.field2, T.field2 ),
field3 = COALESCE( S.field3, T.field3 );
Of course, if there was a single table-valued parameter (as arguable there should be) then the relevance of MERGE is even more obvious.