How does one implement IF-THEN-ELSE in a select statement?
The Oracle decode function acts like a procedural statement inside an SQL statement to return different values or columns based on the values of other columns in the select statement. Some examples: select decode(sex, ‘M’, ‘Male’, ‘F’, ‘Female’, ‘Unknown’) from employees; select a, b, decode( abs(a-b), a-b, ‘a > b’, 0, ‘a = b’, ‘a from tableX; select decode( GREATEST(A,B), A, ‘A is greater than B’, ‘B is greater than A’)… Note: The decode function is not ANSI SQL and is rarely implemented in other RDBMS offerings. It is one of the good things about Oracle, but use it sparingly if portability is required. From Oracle 8i one can also use CASE statements in SQL.
