A good primer about Oracle's CASE Expression:
DECODE is considered the most powerful function in Oracle. Oracle 8i release introduced the CASE expression. The CASE expression can do all that DECODE does plus lot of other things including IF-THEN analysis, use of any comparison operator and checking multiple conditions, all in a SQL query itself. Moreover, using the CASE function, multiple conditions provided in separate SQL queries can be combined into one, thus avoiding multiple statements on the same table (example given below). The function is available from Oracle 8i onwards.
I make no apology for my unabashed love of CASE statements. They are fantastic, and I think everyone should bask in their glory.
No, the above statement was not sarcastic.