SQL - 如何使用 CASE 表达式查询 VIEW - 查找列中的平均数

Question

I am looking to compute the avg win odds and avg place odds of horse racing markets

I have tried a CASE expression since averages for WinOdds should only be calculated if Place =1 and averages for PlaceOdds should only be included when Place <= 10

SELECT 

  CASE WHEN Place = 1 THEN AVG(IndustrySP) AS AvgWinOdds,
  CASE WHEN Place <= 10 THEN AVG((IndustrySP - 1.0) / 5) AS AvgPlaceOdds

FROM dbo.GrandNational -- This is the `view` I want to query

I am looking for average odds for win (when Place =1)

and average odds for place (when Place is <= 10)

Should return something like this:

-- AvgWinOdds   -- AvgPlaceOdds

-- 6.44         -- 4.22

Answer 1

You must average the CASE expressions:

SELECT 
  AVG(CASE WHEN Place = 1 THEN IndustrySP END) AS AvgWinOdds,
  AVG(CASE WHEN Place <= 10 THEN (IndustrySP - 1.0) / 5 END) AS AvgPlaceOdds
FROM dbo.GrandNational