Get slave status using sql query inside if-else condition

Question

How can I stop the slave if it is already running using sql query statements only?

So far I tried to do something like below but getting sql syntax error. I think it is due to the borders of result in conditional statement.

if ((select VARIABLE_VALUE from information_schema.GLOBAL_STATUS 
      where VARIABLE_NAME = 'slave_running')=ON) 
     then  
         STOP SLAVE; 
end if;

Answer 1

Why not simply do STOP SLAVE? If not "slave_running", it will have no effect.

Answer 2

It seems like I have done some mistake in syntax. Forgotten to use DELIMITER

DELIMITER //    
 IF ((select VARIABLE_VALUE from information_schema.GLOBAL_STATUS 
    where VARIABLE_NAME = 'slave_running')='ON') then STOP SLAVE; 
 END IF//    
DELIMITER ;