描述：根据顾客的国家分组，查询顾客数大于5的国家名和顾客数

查询句法：

var 一般分组 = from c in ctx.Customers

group c by c.Country into g

where g.Count() > 5

orderby g.Count() descending

select new

{

国家 = g.Key,

顾客数 = g.Count()

};

对应SQL：

SELECT [t1].[Country], [t1].[value3] AS [顾客数]

FROM (

SELECT COUNT(*) AS [value], COUNT(*) AS [value2], COUNT(*) AS [value3], [t0].[Country]

FROM [dbo].[Customers] AS [t0]

GROUP BY [t0].[Country]

) AS [t1]

WHERE [t1].[value] > @p0

ORDER BY [t1].[value2] DESC

-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [5]

描述：根据国家和城市分组，查询顾客覆盖的国家和城市

查询句法：

var 匿名类型分组 = from c in ctx.Customers

group c by new { c.City, c.Country } into g

orderby g.Key.Country, g.Key.City

select new

{

国家 = g.Key.Country,

城市 = g.Key.City

};

描述：按照是否超重条件分组，分别查询订单数量

查询句法：

var 按照条件分组 = from o in ctx.Orders

group o by new { 条件 = o.Freight > 100 } into g

select new

{

数量 = g.Count(),

是否超重 = g.Key.条件 ? "是" : "否"

};