更新结果GROUP BY

Question

我知道足够的SQL来编写基本的SELECT和UPDATE s。我在努力JOIN s

我想更新犯罪表中的'县'字段。我正在使用一个zip_xref表，它会给我县名。问题在于数百个城市在多个县，我想更新最普遍的县的表，所以我的子查询必须按照大小排列县。

我写这个是为了找到按照每个县的邮政编码排列的县名。

SELECT DISTINCT CountyName AS counties, COUNT(*) AS numZips 
FROM Zip_XRef WHERE (CityName = 'Aurora') AND (StateName = 'Colorado') 
GROUP BY CountyName ORDER BY numZips DESC 

我知道这个更新不起作用，它只是想法。

UPDATE crime_table_08 AS c 
SET county = 
    (SELECT TOP 1 DISTINCT CountyName, COUNT(*) AS numZips 
    FROM Zip_XRef AS z 
    WHERE RTRIM(z.StateName) = RTRIM(c.State) AND RTRIM(z.CityName) = RTRIM(c.city) 
    GROUP BY CountyName ORDER BY numZips DESC 
    ) 

我在想，我需要创建一个临时表，然后调用它来更新C，我不能完全得到我的头周围的逻辑。任何帮助不胜感激。

或者，有没有人认为有更好的办法？

Answer 1

UPDATE c 
SET county = t.CountyName 
FROM crime_table_08 AS c 
CROSS APPLY (
    SELECT TOP (1) CountyName 
    FROM (
     SELECT CountyName, COUNT(*) as cnt 
     FROM Zip_XRef AS z 
     WHERE RTRIM(z.StateName) = RTRIM(c.State) AND RTRIM(z.CityName) = RTRIM(c.city) 
     GROUP BY CountyName) 
    ) AS s 
    ORDER BY cnt DESC) as t;