求帮助，关于mysql触发器的问题，一直语法错误

DELIMITER $$
CREATE TRIGGER t_insert BEFORE INSERT ON bookmanagement.reader
FOR EACH ROW
BEGIN
IF exists(SELECT * FROM reader WHERE readerId=new.readerId)
UPDATE reader SET sum = sum+1 WHERE readerId=new.readerId;
ELSE
INSERT INTO reader(readerId,Name,sex) VALUES(new.readerId,new.Name,new.sex);
END; $$
DELIMITER ;
在插入数据时判断一下能否已存在，若已存在，就对sum属性加1，不存在就插入数据，这样写有错吗

解决方案

DELIMITER $$
CREATE TRIGGER t_insert BEFORE INSERT ON bookmanagement.reader
FOR EACH ROW
BEGIN
IF exists(SELECT * FROM reader WHERE readerId=new.readerId) THEN
UPDATE reader SET sum = sum+1 WHERE readerId=new.readerId;
ELSE
INSERT INTO reader(readerId,Name,sex) VALUES(new.readerId,new.Name,new.sex);
end if;
END; $$
DELIMITER ;