sql - 如何在 SQL Server 中根据地理区域显示平均学校数量

Question

我正在尝试根据地理区域显示学校的平均数量，但我无法计算学校。

这是图表：

SELECT SUM(b) AS sumofarea
FROM 
    (SELECT 
         COUNT(geographic_area_name) AS b,
         geographic_area_name
     FROM 
         geographic_area
     INNER JOIN 
         addresss ON geographic_area.geophic_area_number = addresss.geographic_area_number
     INNER JOIN 
         schools ON addresss.cps_unit = schools.cps_unit
     GROUP BY 
         geographic_area_name) ord;

标签： sqlsql-serverjoinsubqueryaverage