`CASE` expressions in oracle is similar to IF ... THEN ... ELSE logic in SQL statements.
Evaluated in Top to bottom approach, If a condition is true, then corresponding THEN clause is executed and execution jumps to the END CASE clause.

syntax:
```
CASE [ expression ]
WHEN condition_1 THEN result_1
WHEN condition_2 THEN result_2
...
WHEN condition_n THEN result_n
ELSE result
END
```
Example:
```
SELECT emp_name, emp_no, dept_no
(CASE dept_no
WHEN 10 THEN 'ACCOUNTS'
WHEN 20 THEN 'HR'
WHEN 30 THEN 'OPERATIONS'
WHEN 40 THEN 'SALES'
ELSE 'UNKNOWN'
END) DEPARTMENT
FROM EMPLOYEE
ORDER BY emp_name;
```