entity sql count null

Question

我在使用實體SQL計數空值時遇到了問題。

代碼在SQL：

SELECT Table.City, COUNT(*) 
FROM Table 
GROUP BY Table.City 

和LINQ到實體：

var query1 = from g in context.Table 
      group g by g.City into mygroup 
      select new { mygroup, c = mygroup.Count() }; 

都返回正確值：

NULL 4 
Boston 7 
Canberra 1 
London 5 
Melbourne 5 
New York 4 
Paris 15 
Sydney 4 

然而，實體SQL代碼編寫如：

個

string queryString1 = "SELECT city, COUNT(g.City)" + 
         "FROM Entities.Table AS g " + 
         "GROUP BY g.City as city"; 

回報：

NULL 0 
Boston 7 
Canberra 1 
London 5 
Melbourne 5 
New York 4 
Paris 15 
Sydney 4 

爲什麼的NULL不能正確計算？我該如何解決它？

Answer 1

How Entity SQL Differs from Transact-SQL

實體SQL不支持COUNT（*）聚合。改用count（0）。

通常COUNT(*)計數行，而COUNT(g.City)給你NOT NULL值的數量。