Question

I need to write a stored procedure to update one of a set of similar columns. The columns are named ‘UserField1’, ‘UserField2’ etc. I was hoping to pass a parameter to the SPROC which would set the column to be updated. However, I can’t seem to get the code correct. Here’s a simplified example of what I tried (which gets me an ‘Incorrect syntax’ message):

create procedure UpdateUserField
    (@UserFieldNumber int, @UserFieldNewValue int)
as
    update MyTable set
        case @UserFieldNumber
        when 1 then UserField1
        when 2 then UserField2
        end
    = @UserFieldNewValue

Answer 1

What about using a number of IF’s?

CREATE PROCEDURE UpdateUserField
(
    @UserFieldNumber int,
    @UserFieldNewValue int
) AS

IF @UserFieldNumber=1
BEGIN
    UPDATE MyTable SET UserField1 = @UserFieldNewValue
END

IF @UserFieldNumber=2
BEGIN
    UPDATE MyTable SET UserField2 = @UserFieldNewValue
END

Alternatively you can build dynamic SQL in an exec

CREATE PROCEDURE UpdateUserField
(
    @UserFieldNumber int,
    @UserFieldNewValue int
) AS

EXEC('UPDATE MyTable SET UserField' + CONVERT(varchar(10), @UserFieldNumber) + ' = ' + CONVERT(varchar(10), @UserFieldNewValue))

Beware SQL Injection if you do this though, with ints you won’t have a problem, anything else you may need to consider risks.