Creating Column Headings From Data

In this request, they want the last 3 years that anyone was hired to be the column headings.
We need to read the data to get the variables to be used as column headers.

Column Yr1 New_Value Yr1
Column Yr2 New_Value Yr2
Column Yr3 New_Value Yr3

--+- 1 ----------------------------------------------------------------
--| Max will put these all on one line.
--+--------------------------------------------------------------------
Select Max(Case When Rownum = 1 Then Year End) Yr1,
     Max(Case When Rownum = 2 Then Year End) Yr2,
     Max(Case When Rownum = 3 Then Year End) Yr3
From
  --+- 1.1 ----------------------------------------------------------
  --| Get a list of years & put them in order.
  --+----------------------------------------------------------------
    (Select Distinct To_Char(HireDate,'YYYY') Year
       From Emp
      Order By Year Desc
    )
  --+----------------------------------------------------------------
Where Rownum <4;

This will generate a one line report:

YR1  YR2  YR3
---- ---- ----
1987 1982 1981

This sets up the columns to be printed with the format required.

Column '&Yr1' Format $999,999
Column '&Yr2' Format $999,999
Column '&Yr3' Format $999,999

--+- 2 ----------------------------------------------------------------
--| Stack them on lines by department.
--+--------------------------------------------------------------------
Select DeptNo,
     Sum(Case When Year = '&Yr1' Then Sal End) "&Yr1",
     Sum(Case When Year = '&Yr2' Then Sal End) "&Yr2",
     Sum(Case When Year = '&Yr3' Then Sal End) "&Yr3"
From
  --+- 2.1 ----------------------------------------------------------
  --| Convert date & eliminate records not needed.
  --+----------------------------------------------------------------
     (Select To_Char(Hiredate,'YYYY') Year,
             Sal,
             Deptno
        From Emp
       Where To_Char(Hiredate,'YYYY')  In ('&Yr1','&Yr2','&Yr3')
     )
  --+----------------------------------------------------------------
Group By Deptno;

Final Report:

   DEPTNO      1987      1982      1981
--------- --------- --------- ---------
     30 .         .            $9,400
     20    $4,100 .            $5,975
     10 .            $1,300    $7,450