＃1064 - 您的SQL语法有错误;

Question

遇到以下SQL问题，显示错误消息（#1064 - You have an error in your SQL syntax;）但无法确定问题所在。

CREATE TRIGGER name
BEFORE INSERT ON c
FOR EACH ROW
BEGIN
    DECLARE a INT;
    set a = 0;
    WHILE (select count() from c where c.id == a) > 0 DO   
        SET a = a + 1; 
    END WHILE;
    SET new.id = a;
END;