Question

I’m trying to take data from one column, MyTable.SSN, and copy it to another in the same table, MyTable.SSNWithDashes, just formatted differently. If MyTable.SSN doesn’t have exactly 9 digits, I don’t care to process it at all.

I’ve tried this:

IF( SELECT LEN( [SSN] ) FROM [MyTable] ) = 9
UPDATE [MyTable] SET [SSNWithDashes] = LEFT( [SSN], 3 ) + '-' + SUBSTRING( [SSN], 4, 2 ) + '-' + RIGHT( [SSN], 4 ) 
ELSE
UPDATE [MyTable] SET [SSNWithDashes] = NULL

While this works, it throws an error:

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

While I do understand what the warning is saying, I’m not really sure how to go about this differently.

How can I refactor this to remove that warning (and perhaps read a little cleaner)?

Answer 1

UPDATE dbo.[MyTable] 
  SET [SSNWithDashes] = CASE
  WHEN LEN(SSN) = 9 THEN 
    LEFT([SSN],3) + '-' + SUBSTRING([SSN],4,2) + '-' + RIGHT([SSN],4) 
  ELSE NULL
END;