我遇到了这个问题，要找到下表中选民增长最快的地区，即在2001年，2005年和2010年找到地区增长率的最大平均百分比，或者比较每个地区在2001年，2005年和2010年的百分比。
Region Electorate Constituency ElectionYear
-------------- ---------- -------------------------- ------------
South East 109044 Isle of Wight 2010
South East 107737 Isle of Wight 2005
South East 106305 Isle of Wight 2001
North West 90124 Manchester Central 2010
London 89601 East Ham 2010
London 88624 Croydon North 2010
East Midlands 88378 Northampton South 2005
London 88236 Brentford and Isleworth 2005
East Midlands 88058 Daventry 2005
South East 88006 Banbury 2005
East Midlands 86537 Daventry 2001
South West 86324 Devizes 2005
London 85943 Ilford South 2010
London 85851 Kingston and Surbiton 2010
East Midlands 85450 Sleaford and North Hykeham 2010
East Midlands 85271 Northampton South 2001
West Midlands 85241 Stratford-on-Avon 2001
London 85078 West Ham 2010
South West 84821 Bristol West 2001
West Midlands 84540 Stratford-on-Avon 2005
South East 84379 Banbury 2010
London 84049 Brentford and Isleworth 2001
South East 83935 Winchester 2005
London 83904 Harrow East 2005
我试着通过编写这段代码来看这个，但我认为我做的不对;我认为还有其他更好的方法：
SELECT DISTINCT Region, Electorate
FROM DW_FastGrowingElectorateRegion
WHERE Electorate = (SELECT MAX(Electorate) FROM DW_FastGrowingElectorateRegion)
OR Electorate = (SELECT MIN(Electorate) FROM DW_FastGrowingElectorateRegion )
GROUP BY Region, Electorate
ORDER BY Electorate DESC;
结果如下：
Region Electorate
South East 109044
Scotland 31909
任何帮助都会有所帮助，并且非常感谢，因为我花了好几天时间尝试对此进行排序。
谢谢。
答案 0 :(得分：1)
您当前的查询仅选择原始数据中具有[Electorate]最高和最低值的行。您的查询中有一个GROUP BY子句，但您实际上并没有进行任何聚合。
首先在Access中创建一个名为[ElectorateSumsByRegionYear]的已保存查询，如下所示
SELECT
Region,
ElectionYear,
Sum(Electorate) AS SumOfElectorate
FROM DW_FastGrowingElectorateRegion
GROUP BY Region, ElectionYear
对于您提供的测试数据，它会返回
Region ElectionYear SumOfElectorate
-------------- ------------ ---------------
East Midlands 2001 171808
East Midlands 2005 176436
East Midlands 2010 85450
London 2001 84049
London 2005 172140
London 2010 435097
North West 2010 90124
South East 2001 106305
South East 2005 279678
South East 2010 193423
South West 2001 84821
South West 2005 86324
West Midlands 2001 85241
West Midlands 2005 84540
现在我们可以在Access中创建一个名为[ElectorateSumsCurrentPrevious]的已保存查询，以返回结果以及上一期间的相应结果
SELECT
CurrYear.Region,
ElectCurrPrevYr.ElectionYear AS CurrYear,
CurrYear.SumOfElectorate AS CurrSum,
ElectCurrPrevYr.PrevYear,
PrevYear.SumOfElectorate AS PrevSum
FROM
(
ElectorateSumsByRegionYear AS CurrYear
INNER JOIN
(
SELECT t1.Region, t1.ElectionYear, Max(t2.ElectionYear) AS PrevYear
FROM
ElectorateSumsByRegionYear AS t1
INNER JOIN
ElectorateSumsByRegionYear AS t2
ON t1.Region = t2.Region
AND t1.ElectionYear > t2.ElectionYear
GROUP BY t1.Region, t1.ElectionYear
) AS ElectCurrPrevYr
ON (CurrYear.ElectionYear = ElectCurrPrevYr.ElectionYear)
AND (CurrYear.Region = ElectCurrPrevYr.Region)
)
INNER JOIN
ElectorateSumsByRegionYear AS PrevYear
ON (ElectCurrPrevYr.PrevYear = PrevYear.ElectionYear)
AND (ElectCurrPrevYr.Region = PrevYear.Region);
返回
Region CurrYear CurrSum PrevYear PrevSum
-------------- -------- ------- -------- -------
East Midlands 2005 176436 2001 171808
East Midlands 2010 85450 2005 176436
London 2005 172140 2001 84049
London 2010 435097 2005 172140
South East 2005 279678 2001 106305
South East 2010 193423 2005 279678
South West 2005 86324 2001 84821
West Midlands 2005 84540 2001 85241
我们可以使用该查询作为任何＆＃34;增长的基础＆＃34;我们想要使用的衡量标准，例如
SELECT
Region,
CurrYear,
CurrSum,
PrevYear,
PrevSum,
[CurrSum]-[PrevSum] AS Increase,
(CDbl([CurrSum])/CDbl([PrevSum]))^(1/([CurrYear]-[PrevYear]))-1 AS AvgAnnualGrowthRate
FROM ElectorateSumsCurrentPrevious;
返回
Region CurrYear CurrSum PrevYear PrevSum Increase AvgAnnualGrowthRate
-------------- -------- ------- -------- ------- -------- ---------------------
East Midlands 2005 176436 2001 171808 4628 6.66728558280982E-03
East Midlands 2010 85450 2005 176436 -90986 -0.134982342500498
London 2005 172140 2001 84049 88091 0.19629231270215
London 2010 435097 2005 172140 262957 0.20376263338977
South East 2005 279678 2001 106305 173373 0.273579774134796
South East 2010 193423 2005 279678 -86255 -7.10978631581222E-02
South West 2005 86324 2001 84821 1503 4.40078147996426E-03
West Midlands 2005 84540 2001 85241 -701 -2.06230641894412E-03
编辑重新评论
如果您想要一个只返回最高和最低增长率的查询，请将上述查询保存为[ElectorateGrowthByRegionYear]，然后使用类似
的内容 SELECT TOP 1 * FROM ElectorateGrowthByRegionYear
ORDER BY AvgAnnualGrowthRate DESC
UNION ALL
SELECT TOP 1 * FROM ElectorateGrowthByRegionYear
ORDER BY AvgAnnualGrowthRate ASC