mysql - 获取一些行和总数的存储过程

Question

我是 sql 新手，所以我需要你的帮助!我需要一个存储过程来获取一定数量的文章，其中有一些偏移量和它们的总数来进行分页......这是正确的代码还是有更好的方法？将执行多少查询，ctid 1 个，总计 1 个，内容数据 1 个？？

DELIMITER $$
CREATE PROCEDURE `getArticles`(`offset` INT, `count` INT)
BEGIN
  DECLARE ctid, total INT;
  SET ctid = (SELECT id FROM content_types WHERE name='article');
  SET total = (SELECT COUNT(*) FROM content WHERE content_type = ctid);  
  SELECT *, total FROM content 
    WHERE content_type = ctid 
    LIMIT count 
    OFFSET offset;
END $$
DELIMITER ;

Answer 1

您可以尝试利用 SQL_CALC_FOUND_ROWS 选项和 FOUND_ROWS()功能

SQL_CALC_FOUND_ROWS and FOUND_ROWS() can be useful in situations when you want to restrict the number of rows that a query returns, but also determine the number of rows in the full result set without running the query again. An example is a Web script that presents a paged display containing links to the pages that show other sections of a search result. Using FOUND_ROWS() enables you to determine how many other pages are needed for the rest of the result.

话虽如此，您的程序可能看起来像

DELIMITER $$
CREATE PROCEDURE get_articles(IN _offset INT, IN _count INT, OUT _total INT)
BEGIN
  SELECT SQL_CALC_FOUND_ROWS * 
    FROM content c JOIN content_types t 
      ON c.content_type = t.id
   WHERE t.name = 'article' 
    LIMIT _offset, _count;
  SET _total = FOUND_ROWS();
END$$
DELIMITER ;

示例用法:

SET @total = 0;
CALL get_articles(0, 3, @total);
SELECT @total;

这是 SQLFiddle 演示