Question

我正在调试一些代码并遇到以下SQL查询（简化版）：

SELECT ads.*, location.county 
FROM ads
LEFT JOIN location ON location.county = ads.county_id
WHERE ads.published = 1 
AND ads.type = 13
AND ads.county_id = 2
OR ads.county_id = 5
OR ads.county_id = 7
OR ads.county_id = 9

我从查询得到了非常奇怪的结果，我认为它是因为第一个OR否定了之前找到的AND运算符。

这样可以获得所有类型广告的结果，而不仅仅是类型13的结果。

每次调用查询时，可能需要查找不同数量的县实体。

任何有关正确方法的帮助都将受到赞赏。

Answer 1

将括号括在“OR”周围：

SELECT ads.*, location.county 
FROM ads
LEFT JOIN location ON location.county = ads.county_id
WHERE ads.published = 1 
AND ads.type = 13
AND
(
    ads.county_id = 2
    OR ads.county_id = 5
    OR ads.county_id = 7
    OR ads.county_id = 9
)

甚至更好，使用IN：

SELECT ads.*, location.county 
FROM ads
LEFT JOIN location ON location.county = ads.county_id
WHERE ads.published = 1 
AND ads.type = 13
AND ads.county_id IN (2, 5, 7, 9)

Answer 2

您可以尝试在OR表达式周围使用括号，以确保正确解释您的查询，或者更简洁地使用IN：

SELECT ads.*, location.county 
FROM ads
LEFT JOIN location ON location.county = ads.county_id
WHERE ads.published = 1 
AND ads.type = 13
AND ads.county_id IN (2,5,7,9)

Answer 3

使用IN更简单：

SELECT ads.*, location.county 
  FROM ads
  LEFT JOIN location ON location.county = ads.county_id
  WHERE ads.published = 1 
        AND ads.type = 13
        AND ads.county_id IN (2,5,7,9)

如何从x等于多个值中选择？

3 个答案: