Question

假设我有以下Oracle数据库表user_data：

USER    Manager     Country
User 1  Manager 1   Canada
User 2  Manager 2   Canada
User 3  Manager 3   Canada
User 4  Manager 1   England
User 5  Manager 1   Scotland
User 6  Manager 1   Scotland
User 7  Manager 1   Scotland
User 8  Manager 1   England

我们有一项业务规则，即如果经理只是该国用户的唯一经理，则该经理只负责一个国家/地区。例如，根据提供的数据，经理1仅负责苏格兰和英格兰，但不负责加拿大。我有一个解决方案，但它很慢，我认为必须有更好的方法来查询数据：

SELECT DISTINCT manager, country
FROM user_data
WHERE country IN (
    SELECT country FROM (
        SELECT DISTINCT country, manager
        FROM user_data
    )
    GROUP BY country
    HAVING count(country) = 1
);

更高效查询的任何想法，确定哪个经理负责一个国家/地区？

Answer 1

您可以尝试使用left join和is not null：

select distinct t1.manager
from user_data t1
left join (
    select country
    from user_data 
    group by country
    having count(distinct manager) = 1) t2 on t1.country = t2.country
where t2.country is not null

Answer 2

检查stragg（）函数这可能是hepl，我没有在sql下面测试过。

SELECT  stragg(manager), country
FROM user_data
GROUP BY country
HAVING count(country) = 1

按国家/地区计算不同的经理人

2 个答案: