mysql - 创建一个触发器以计算记录数

Question

我的表与“图书”相关，我想在特定列中的特定条件中找到多少条记录

{DELIMITER $$
CREATE TRIGGER No_of_Publisher_year After Insert ON Books FOR EACH ROW Set @Count_NO=@Count_NO + New.Copyright Begin
    SELECT Count(@Count_NO) AS 'No_of_publisher_in_year_2007' FROM Books WHERE Copyright=2007;

END; $$ 
DELIMITER ;}

我收到一个错误：


  1064-您的SQL语法有误；检查与您的MySQL服务器版本对应的手册以获取正确的语法，以在第2行的'SELECT Count（@Count_NO）AS'No_of_publisher_in_year_2007'FROM Books WHERE Copyr'附近使用

Answer 1

您需要像下面修改触发器主体

CREATE TRIGGER No_of_Publisher_year 
After Insert ON Books 
FOR EACH ROW 
Begin
Set @Count_NO := @Count_NO + New.Copyright;
    SELECT Count(*) AS 'No_of_publisher_in_year_2007' 
    FROM Books WHERE Copyright=2007;
END;