sql - 使用 IN() 和强制值的 SQL 查询

Question

我有一个 INNER JOIN 查询，它根据连接表中的值获取国家/地区名称：

SELECT DISTINCT countryName, countrySlug
FROM countries AS Country
INNER JOIN countries_networks AS n ON Country.id = n.country_id
AND n.network_id IN ( 6, 7, 8, 9, 14 ) 

但是，我现在需要select满足IN() 标准的那些，并且还必须包含网络 2。

我显然不能只在 IN() 中添加 2，因为我需要 2 是强制性的，并且至少需要其中一个。

有人可以帮忙吗，我觉得它非常简单。

Answer 1

试试这个：

SELECT DISTINCT 
  countryName, 
  countrySlug
FROM countries AS Country
INNER JOIN countries_networks AS n  ON Country.id   = n.country_id
                                   AND n.network_id IN (6, 7, 8, 9, 14) 
WHERE Country.id IN (SELECT id
                     FROM countries_networks 
                     WHERE network_id = 2
                       AND id IS NOT NULL);

这将确保任何选定的国家/地区都必须拥有network_id = 2.

Answer 2

首先，通过用子查询DISTINCT替换连接来删除。EXISTS然后您可以添加另一个子查询来处理额外的要求：

SELECT countryName, countrySlug
FROM countries AS c
WHERE EXISTS
      ( SELECT *
        FROM countries_networks AS n 
        WHERE c.id = n.country_id
          AND n.network_id IN ( 6, 7, 8, 9, 14 )
      )
  AND EXISTS
      ( SELECT *
        FROM countries_networks AS n 
        WHERE c.id = n.country_id
          AND n.network_id = 2
      ) ;

Answer 3

试试这个（双重加入？）：

SELECT DISTINCT countryName, countrySlug, n.country_id, n2.country_id
FROM countries AS Country
INNER JOIN countries_networks AS n ON Country.id = n.country_id
AND n.network_id
IN ( 6, 7, 8, 9, 14 )
INNER JOIN countries_networks AS n2 ON Country.id = n2.country_id
AND n2.network_id = 2

注意：显示的n.country_id, n2.country_id值仅用于能够检查结果

Answer 4

只需这样做：

SELECT DISTINCT countryName, countrySlug
FROM countries AS Country
INNER JOIN countries_networks AS n ON Country.id = n.country_id
AND n.network_id=2 And n.network_id IN (2, 6, 7, 8, 9, 14 )