entity sql count null
问题描述:
我在使用实体SQL计数空值时遇到了问题。entity sql count null
代码在SQL:
SELECT Table.City, COUNT(*)
FROM Table
GROUP BY Table.City
和LINQ到实体:
var query1 = from g in context.Table
group g by g.City into mygroup
select new { mygroup, c = mygroup.Count() };
都返回正确值:
NULL 4
Boston 7
Canberra 1
London 5
Melbourne 5
New York 4
Paris 15
Sydney 4
然而,实体SQL代码编写如:
个string queryString1 = "SELECT city, COUNT(g.City)" +
"FROM Entities.Table AS g " +
"GROUP BY g.City as city";
回报:
NULL 0
Boston 7
Canberra 1
London 5
Melbourne 5
New York 4
Paris 15
Sydney 4
为什么的NULL不能正确计算?我该如何解决它?
答
How Entity SQL Differs from Transact-SQL
实体SQL不支持COUNT(*)聚合。改用count(0)。
通常COUNT(*)
计数行,而COUNT(g.City)
给你NOT NULL值的数量。
工作正常。谢谢。 –