LINQ  to SQL 语句(3) 之  Count/Sum/Min/Max/Avg [1] Count/Sum 讲解 [2] Min 讲解 [3] Max 讲解 [4] Average 和 Aggregate 讲解 Count/Sum/Min/Max/Avg 操作符 适用场景: 统计数据吧,比如统计一些数据的个数,求和,最小值,最大值,平均数. Count 说明:返回集合中的元素个数,返回 INT 类型:不延迟.生成  SQL 语句为:SELECT COUNT(*) FROM 1.简单形式:…

oracle通过sql随机取表中的10条记录: SELECT * FROM (SELECT * FROM T_USER ORDER BY DBMS_RANDOM.RANDOM()) WHERE Rownum <= 10;…

适用场景:统计数据吧,比如统计一些数据的个数,求和,最小值,最大值,平均数. Count 说明:返回集合中的元素个数,返回INT类型:不延迟.生成SQL语句为:SELECT COUNT(*) FROM 1.简单形式: 得到数据库中客户的数量: var q = db.Customers.Count(); 2.带条件形式: 得到数据库中未断货产品的数量: var q = db.Products.Count(p => !p.Discontinued); LongCount 说明:返回集合中的元素个数,…

1.sqlserer 中有一张父子关系表,表结构如下: CREATE TABLE [dbo].[testparent]( [ID] [int] IDENTITY(1,1) NOT NULL, [name] [nvarchar](50) NULL, [parentID] [int] NULL, CONSTRAINT [PK_testparent] PRIMARY KEY CLUSTERED 2.其中的数据类似: 3.用 CET 递归的方式返回每条记录的层级,其中 lev 为层级, where 后面…

一.首先,新建三张表 DROP TABLE IF EXISTS `article`; CREATE TABLE `article` ( `id` ) unsigned NOT NULL AUTO_INCREMENT, `title` ) NOT NULL COMMENT '标题', `content` text NOT NULL COMMENT '内容', PRIMARY KEY (`id`) ) ENGINE DEFAULT CHARSET=utf8 COMMENT='文章表'; -- --…

1. select sum(CASE WHEN A.[STATUS]=0 THEN 1 ELSE 0 end) as a1,  sum(CASE A.[STATUS] WHEN 1 THEN 1 ELSE 0 end) as a2,  sum(CASE A.[STATUS] WHEN 2 THEN 1 ELSE 0 end) as a3, A.UserId,C.TrainId  from CoursewareLogMiddle A join LessonDetail B   on A.Lesso…

----------用来双重排序,且获取唯一 go SELECT ROW_NUMBER() OVER (ORDER BY AScore DESC,ATime ASC) AS Rank, * FROM ( SELECT AScore,ATime,MerchantWeixinUserID, ROW_NUMBER() OVER (partition by MerchantWeixinUserID order by ASCORE DESC,ATime ASC) AS SX FROM ( ),Create…

1.初始化数据 create table Products ( id ,), name ), categroy int, addtime datetime , ) insert into Products (name ,categroy,addtime) values (,'2016-10-01 00:00:00.000'), (,'2016-10-02 00:00:00.000'), (,'2016-10-03 00:00:00.000'), (,'2016-10-01 00:00:00.00…

Northwind数据库,选取价格第二高的产品. 有两种方法,一个是用Row_Number()函数: SELECT productname FROM ( productname, Row_Number() OVER (ORDER BY unitprice desc) AS rownum FROM Products) AS tbl ; 另一种是对子语句的的结果再进行排序: productname FROM ( productname,unitprice FROM Products order by…

select s.*  from (     select *, row_number() over (partition by PersonnelAccount order BY PersonnelID) as group_idx      from AUX_SpecialPersonnel ) swhere s.group_idx > 1…