SQL UPDATE statement to switch two values in two rows

Question

I'm using SQL Server to swap two values in two rows. Let me show:

[ord] [name]
1     John
4     Jack
7     Pete
9     Steve
11    Mary

Say, I need to swap [ord] numbers for "Pete" and "Steve" to make this table to be like so:

[ord] [name]
1     John
4     Jack
9     Pete
7     Steve
11    Mary

This seems like a trivial task but I can't seem to write an SQL UPDATE statement for it.

Answer 1

If 'Peter' and 'Steve' are unique in your table, this will do:

UPDATE TableX
SET ord = ( SELECT MIN(ord) + MAX(ord) 
            FROM TableX 
            WHERE name IN ('Peter', 'Steve')
          ) - ord
WHERE name IN ('Peter', 'Steve')

or (improved by @Erwin):

UPDATE TableX
SET ord = ( SELECT SUM(ord) 
            FROM TableX 
            WHERE name IN ('Peter', 'Steve')
          ) - ord
WHERE name IN ('Peter', 'Steve')

Answer 2

Use a CASE expression:

UPDATE yourtable
SET [ord] = CASE [ord] WHEN 9 THEN 7
                       WHEN 7 THEN 9 END
WHERE [ord] IN (7, 9)