Decode Function and Case Statement are used to transform data values at retrieval time. DECODE and CASE are both analogous to the "IF THEN ELSE" conditional statement.

Before version 8.1, the DECODE was the only thing providing IF-THEN-ELSE functionality in Oracle SQL. Because DECODE can only compare discrete values (not ranges), continuous data had to be contorted into discreet values using functions like FLOOR and SIGN. In...