更新結果GROUP BY

Question

我知道足夠的SQL來編寫基本的SELECT和UPDATE s。我在努力JOIN s

我想更新犯罪表中的'縣'字段。我正在使用一個zip_xref表，它會給我縣名。問題在於數百個城市在多個縣，我想更新最普遍的縣的表，所以我的子查詢必須按照大小排列縣。

我寫這個是爲了找到按照每個縣的郵政編碼排列的縣名。

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

我知道這個更新不起作用，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，我需要創建一個臨時表，然後調用它來更新C，我不能完全得到我的頭周圍的邏輯。任何幫助不勝感激。

或者，有沒有人認爲有更好的辦法？

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;