将空白结果设置为等于SQL Server中的特定字符串

Question

I have a query that returns a result set which contains a certain column that needs some tweaking. Basically, in the result set, there are certain rows that contain a blank value for the applicable column. What I need to do is set all instances of that blank value to a specific string. I have tried declaring a variable and setting the variable equal to the column name (using a SELECT statement) and then using an IF statement to set the value to a specific string if it is blank (' '). My code thus far is as follows:

declare @sourceNode varchar(30)                  
set @sourceNode = (select sn_name from pt_cust)
if @sourceNode = '' begin
    set @sourceNode = 'None'
end  

This code returns an error stating that the sub-query returns more than 1 value. This seems like an easy task but I am stuck at the moment. How can this be accomplished?

Answer 1

This is a case (heh) for CASE:

SELECT CASE WHEN sn_name = '' THEN 'None' ELSE sn_name END
FROM pt_cust

You are getting the error message you mentioned because your SELECT statement can return more than one row, in which case it can not be assigned to a variable.