A literal in the Projection clause

The following query uses a literal in the projection list to tag the output of part of a union so it can be distinguished later. The tag is given the label sortkey. The query uses sortkey to order the retrieved rows.
Figure 1: Query
SELECT '1' sortkey, lname, fname, company, 
     city, state, phone 
   FROM customer x
   WHERE state = 'CA'
UNION
SELECT '2' sortkey, lname, fname, company, 
     city, state, phone 
   FROM customer y
   WHERE state <> 'CA'
   INTO TEMP calcust;
SELECT * FROM calcust
   ORDER BY 1;
The query creates a list in which the customers from California appear first.
Figure 2: Query result
sortkey  1
lname    Baxter
fname    Dick
company  Blue Ribbon Sports
city     Oakland
state    CA
phone    415-655-0011

sortkey  1
lname    Beatty
fname    Lana
company  Sportstown
city     Menlo Park
state    CA
phone    415-356-9982
⋮
sortkey  2
lname    Wallack
fname    Jason
company  City Sports
city     Wilmington
state    DE
phone    302-366-7511