MySQL foreach替代程序

Question

我的问题很简单.我有sets一个存储产品集的表(更多的产品看起来像外面的一个 - 电脑,鼠标和键盘,例如)它使用sets_products表到products表连接M:N . 每个产品都可以有参数(再次连接M:N).

我有一个程序,它生成所有参数作为字符串(对于搜索缓存 - 如'hdd:120GB,LCD:1440:900,..'),但现在我需要遍历集合的产品并调用每个的程序他们.我不能用PHP做,因为它用于触发器.

我想用这样的东西(伪SQL)

FOREACH(SELECT products_id FROM sets_products WHERE set_id = 1)
    generate_parameter_list(product_id,@result)
    @param = CONCAT(@param,",",@result);
END FOREACH;

这可以在MySQL中完成吗？

Answer 1

这是游标的mysql参考.所以我猜它是这样的:

  DECLARE done INT DEFAULT 0;
  DECLARE products_id INT;
  DECLARE result varchar(4000);
  DECLARE cur1 CURSOR FOR SELECT products_id FROM sets_products WHERE set_id = 1;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

  OPEN cur1;

  REPEAT
    FETCH cur1 INTO products_id;
    IF NOT done THEN
      CALL generate_parameter_list(@product_id, @result);
      SET param = param + "," + result; -- not sure on this syntax
    END IF;
  UNTIL done END REPEAT;

  CLOSE cur1;

  -- now trim off the trailing , if desired

Answer 2

这可以通过MySQL完成,尽管它非常不直观:

CREATE PROCEDURE p25 (OUT return_val INT)
BEGIN
  DECLARE a,b INT;
  DECLARE cur_1 CURSOR FOR SELECT s1 FROM t;
  DECLARE CONTINUE HANDLER FOR NOT FOUND
  SET b = 1;
  OPEN cur_1;
  REPEAT
    FETCH cur_1 INTO a;
    UNTIL b = 1
  END REPEAT;
  CLOSE cur_1;
  SET return_val = a;
END;//

查看本指南:mysql-storedprocedures.pdf