Question

我正在尝试合并3个选择语句的结果，这些语句将从不同的食物类别中选择不同的食物名称。然而，我的桌子很少有“foodItems”的例子。我需要为每个select语句只选择1个项目，我希望它是随机完成的。我不太确定如何实现我已经尝试在每个select语句的末尾插入ORDER BY RAND() LIMIT 1但MySQL不喜欢它。有人可以提供帮助

SELECT foodName
FROM food
WHERE foodCategory_id = 1 OR 2
UNION
SELECT foodName
FROM food
WHERE foodCategory_id = 7 OR 8 OR 9
UNION
SELECT foodName
FROM food
WHERE foodCategory_id = 10 OR 11

Answer 1

SELECT foodname FROM food WHERE .. ORDER BY RAND() LIMIT 0,1;

只需添加您想要的任何条件。

Answer 2

您可以创建一个外部SQL，其中from子句是某种临时表，如下所示：

 SELECT food_name from (
  SELECT foodName
  FROM food
  WHERE foodCategory_id = 1 OR 2
  ORDER BY RAND() limit 1) a
 UNION
 SELECT food_name from (
  SELECT foodName
  FROM food
  WHERE foodCategory_id = 7 OR 8 OR 9
  ORDER BY RAND() limit 1) b
 UNION
 SELECT food_name from (
  SELECT foodName
  FROM food
  WHERE foodCategory_id = 10 OR 11
  ORDER BY RAND() limit 1) c

如何在MySQL中结合使用Rand功能

2 个答案: