Use CASE statement : CASE « PL SQL Statements « Oracle PL/SQL Tutorial

SQL>
SQL> CREATE TABLE books (
  2    isbn      CHAR(10) PRIMARY KEY,
  3    category  VARCHAR2(20),
  4    title     VARCHAR2(100),
  5    num_pages NUMBER,
  6    price     NUMBER,
  7    copyright NUMBER(4)
  8  );

Table created.

SQL>
SQL> INSERT INTO books (isbn, category, title, num_pages, price, copyright)
  2    VALUES ('72122048', 'Oracle Basics', 'Oracle8i: A Beginner''s Guide', 765, 44.99, 1999);

1 row created.

SQL>
SQL>
SQL>
SQL> SET SERVEROUTPUT ON ESCAPE OFF
SQL>
SQL> DECLARE
  2     v_category books.category%TYPE;
  3     v_discount NUMBER(10,2);
  4     v_isbn books.isbn%TYPE := '72230665';
  5  BEGIN
  6     SELECT category
  7     INTO v_category
  8     FROM books
  9     WHERE isbn = v_isbn;
 10
 11     -- Determine discount based on category
 12     CASE v_category
 13     WHEN 'Oracle Basics'
 14        THEN v_discount := .15;
 15     WHEN 'Oracle Server'
 16        THEN v_discount := .10;
 17     END CASE;
 18
 19     DBMS_OUTPUT.PUT_LINE('The discount is '||v_discount*100||' percent');
 20  EXCEPTION
 21     WHEN OTHERS
 22     THEN
 23        DBMS_OUTPUT.PUT_LINE(SQLERRM);
 24  END;
 25  /
ORA-01403: no data found

PL/SQL procedure successfully completed.

SQL>
SQL>
SQL> UPDATE books
  2  SET category = 'Oracle Programming'
  3  WHERE isbn = '72230665';

0 rows updated.

SQL> COMMIT;

Commit complete.

SQL>
SQL> DECLARE
  2     v_category books.category%TYPE;
  3     v_discount NUMBER(10,2);
  4     v_isbn books.isbn%TYPE := '72230665';
  5  BEGIN
  6     SELECT category
  7     INTO v_category
  8     FROM books
  9     WHERE isbn = v_isbn;
 10
 11     -- Determine discount based on category
 12     CASE v_category
 13     WHEN 'Oracle Basics'
 14        THEN v_discount := .15;
 15     WHEN 'Oracle Server'
 16        THEN v_discount := .10;
 17     ELSE v_discount := .5;
 18     END CASE;
 19
 20     DBMS_OUTPUT.PUT_LINE('The discount is '||v_discount*100||' percent');
 21  EXCEPTION
 22     WHEN OTHERS
 23     THEN
 24        DBMS_OUTPUT.PUT_LINE(SQLERRM);
 25  END;
 26  /
ORA-01403: no data found

PL/SQL procedure successfully completed.

SQL>
SQL> drop table books;

Table dropped.

22.2.CASE
	22.2.1.	CASE statements
	22.2.2.	When creating selector CASE statements, you cannot have NULL in the list of possible values.
	22.2.3.	Use CASE statement
	22.2.4.	Named case block
	22.2.5.	case when
	22.2.6.	An example of comparison of two numbers using a searched CASE expression
	22.2.7.	Variable assignment with case statement
	22.2.8.	Use case statement in a dbms_output.put_line
	22.2.9.	Simple CASE statement with range
	22.2.10.	Case statement to call procedure
	22.2.11.	Return statement with case
	22.2.12.	Use case statement in procedure call to use the proper parameter value