if else in oracle sql query example

1DECLARE 
2   a number(3) := 100; 
3BEGIN 
4   IF ( a = 10 ) THEN 
5      dbms_output.put_line('Value of a is 10' ); 
6   ELSIF ( a = 20 ) THEN 
7      dbms_output.put_line('Value of a is 20' ); 
8   ELSIF ( a = 30 ) THEN 
9      dbms_output.put_line('Value of a is 30' ); 
10   ELSE 
11       dbms_output.put_line('None of the values is matching'); 
12   END IF; 
13   dbms_output.put_line('Exact value of a is: '|| a );  
14END; 
15/ 

1IF condition1 THEN
2   {...statements to execute when condition1 is TRUE...}
3
4ELSIF condition2 THEN
5   {...statements to execute when condition1 is FALSE and condition2 is TRUE...}
6
7ELSE
8   {...statements to execute when both condition1 and condition2 are FALSE...}
9
10END IF;