The continuing saga of Ian trying to learn DB2-SQL

18. CASE Statements

Are these even possible:

SELECT
   CASE
   WHEN v.id=1 THEN 'Hello';
   WHEN v.id=2 THEN ', ';
   WHEN v.id=3 THEN 'world';
   ELSE '!'
   END CASE AS foo
FROM (VALUES 1, 2, 3, 4) AS v(id)

Desired output
   foo
   ========
   Hello
   ,
   world
   !

Another example:
   SELECT
       CustomerID,
       SUM(
           CASE
           WHEN OrderValue > 1000 THEN OrderAmount;
           ELSE 0
           END CASE) AS TotalOfBigOrders
   FROM Orders

Another example:

   SELECT
       i.InfractionID,
       CASE
           WHEN i.EmployeeID IS NOT NULL THEN (Employees.EmployeeName);
           WHEN i.PatronID IS NOT NULL THEN (Patrons.PatronName);
           ELSE 'Unknown Participant';
           END CASE AS PersonDoingTheInfaction
   FROM Infactions i
       LEFT JOIN Patrons
       ON i.PatronID = Patrons.PatronID
       LEFT JOIN Employees
       ON i.EmployeeID = Employees.EmployeeID

or another desired technique of the above:

SELECT
   i.InfactionID,
   CASE
       WHEN i.EmployeeID IS NOT NULL THEN (
           SELECT EmployeeName
           FROM Employees
           WHERE Employees.EmployeeID = i.EmployeeID);
       WHEN i.PatronID IS NOT NULL THEN (
           SELECT Patronname
           FROM Patrons
           WHERE Patrons.PatronsID = i.PatronID);
       ELSE 'Unknown participant';
       END CASE AS PersonDoingTheInfraction
FROM Infractions i