CASE WHEN字段的平均值

Question

如何获取TotalTeamMembership列的平均值？

SELECT Player,
CASE WHEN Basketball = '' THEN 0 ELSE 1 END + 
CASE WHEN Baseball = '' THEN 0 ELSE 1 END + 
CASE WHEN Football = '' THEN 0 ELSE 1 END AS TotalTeamMembership
FROM PlayerMembership;

这是我目前得到的：

这就是我需要的：

谢谢您的指导！

Answer 1

您可以使用AVG()：

SELECT AVG(CASE WHEN Basketball = '' THEN 0.0 ELSE 1 END + 
           CASE WHEN Baseball = '' THEN 0 ELSE 1 END + 
           CASE WHEN Football = '' THEN 0 ELSE 1 END
           ) AS avg_TotalTeamMembership
FROM PlayerMembership;

Answer 2

您可以使用AVG聚合函数：

SELECT AVG(TotalTeamMembership)
FROM (SELECT Player,
       CASE WHEN Basketball = '' THEN 0 ELSE 1 END + 
       CASE WHEN Baseball = '' THEN 0 ELSE 1 END + 
       CASE WHEN Football = '' THEN 0 ELSE 1 END AS TotalTeamMembership
      FROM PlayerMembership) s;