DELIMITER $$
CREATE TRIGGER clickOnce
BEFORE INSERT ON clicks
for each row
if((select count(*) from clicks where adoptableID=new.adoptableID and userID=new.userID)<1) then
   insert into clicks(userID,adoptableID,lastClick)
   values(new.userID,new.adoptableID,new.lastClick);
else if(addtime((select lastClick from clicks where adoptableID=new.adoptableID and userID=new.userID),'24:00') < CURRENT_TIMESTAMP) then
 update clicks
 set lastClick=new.lastClick
 where userID=new.userID
 and adoptableID=new.adoptableID;
else
 signal sqlstate '45000' set message_text='You must wait one day between clicks.'
end if;
END$$
DELIMITER ;