Question

我必须为以下情况编写一个通用的sql查询：

city_id, person_id
0           0
1           1
0           2
1           3
0           3
0           4
1           4
1           5
0           6
0           7

我必须只选择属于0和1城市的人，如果新城市和新人进入，那么只选择那些属于所有城市的人。

Answer 1

要查找属于城市0和城市1的人，如果这些是您正在查看的唯一两个城市：

SELECT person_id,
       COUNT(*)
FROM table
GROUP BY person_id
HAVING COUNT(*) > 1

这将显示所有具有多条记录的person_id值（例如它们属于多个城市的位置。）

如果您有两个以上城市，则可以按城市进一步细化：

SELECT person_id,
       COUNT(*)
FROM table
WHERE city_id IN (0, 1) -- or any city configuration you need.
GROUP BY person_id
HAVING COUNT(*) > 1

Answer 2

类似以下内容：

SELECT person_id
FROM table 
GROUP BY person_id
HAVING COUNT(*) > (
  (SELECT COUNT(DISTINCT city_id) FROM table
  )-1);

我希望它可以帮助别人。

Answer 3

此查询并未对数据库中有多少个城市做出任何假设。

select person_id from T
where city_id in (0, 1)
group by person_id
having count(distinct city_id) = 2 /* distinct isn't necessary if city_id is guaranteed unique per person */

Answer 4

如果您的city_id是自动增量。像这样的东西也会起作用。

SELECT person_id
FROM table 
GROUP BY person_id
HAVING COUNT(*) > (SELECT MAX(city_id) FROM cities)+1;

如何编写通用SQL select语句来选择属于所有城市的人

4 个答案: