sql 、linq、lambda 查询语句的区别
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了sql 、linq、lambda 查询语句的区别,小编现在分享给大家,供广大互联网技能从业者学习和参考。文章包含4282字,纯文字阅读大概需要7分钟。
内容图文
select * from student Linq: from s in Students select s Lambda: Students.Select( s => s)2 按条件查询全部:
实例 Code 查询Student表中的所有记录的Sname、Ssex和Class列。 select sname,ssex,class from student Linq: from s in Students select new { s.SNAME, s.SSEX, s.CLASS } Lambda: Students.Select( s => new { SNAME = s.SNAME,SSEX = s.SSEX,CLASS = s.CLASS })View Code
3.distinct 去掉重复的
实例 Code 查询教师所有的单位即不重复的Depart列。 select distinct depart from teacher Linq: from t in Teachers.Distinct() select t.DEPART Lambda: Teachers.Distinct().Select( t => t.DEPART)View Code
4.连接查询 between and
实例 Code 查询Score表中成绩在60到80之间的所有记录。 select * from score where degree between 60 and 80 Linq: from s in Scores where s.DEGREE >= 60 && s.DEGREE < 80 select s Lambda: Scores.Where( s => ( s.DEGREE >= 60 && s.DEGREE < 80 ) )View Code
5.在范围内筛选 In
实例 Code select * from score where degree in (85,86,88) Linq: from s in Scores where ( new decimal[]{85,86,88} ).Contains(s.DEGREE) select s Lambda: Scores.Where( s => new Decimal[] {85,86,88}.Contains(s.DEGREE))View Code
6.or 条件过滤
实例 Code 查询Student表中"95031"班或性别为"女"的同学记录。 select * from student where class =‘95031‘ or ssex= N‘女‘ Linq: from s in Students where s.CLASS == "95031" || s.CLASS == "女" select s Lambda: Students.Where(s => ( s.CLASS == "95031" || s.CLASS == "女"))View Code
7.排序
实例 Code 以Class降序查询Student表的所有记录。 select * from student order by Class DESC Linq: from s in Students orderby s.CLASS descending select s Lambda: Students.OrderByDescending(s => s.CLASS)View Code
8.count()行数查询
实例 Code select count(*) from student where class = ‘95031‘ Linq: ( from s in Students where s.CLASS == "95031" select s ).Count() Lambda: Students.Where( s => s.CLASS == "95031" ) .Select( s => s) .Count()View Code
9.avg()平均
实例 Code 查询‘3-105‘号课程的平均分。 select avg(degree) from score where cno = ‘3-105‘ Linq: ( from s in Scores where s.CNO == "3-105" select s.DEGREE ).Average() Lambda: Scores.Where( s => s.CNO == "3-105") .Select( s => s.DEGREE)View Code
10.子查询
实例 Code 查询Score表中的最高分的学生学号和课程号。 select distinct s.Sno,c.Cno from student as s,course as c ,score as sc where s.sno=(select sno from score where degree = (select max(degree) from score)) and c.cno = (select cno from score where degree = (select max(degree) from score)) Linq: ( from s in Students from c in Courses from sc in Scores let maxDegree = (from sss in Scores select sss.DEGREE ).Max() let sno = (from ss in Scores where ss.DEGREE == maxDegree select ss.SNO).Single().ToString() let cno = (from ssss in Scores where ssss.DEGREE == maxDegree select ssss.CNO).Single().ToString() where s.SNO == sno && c.CNO == cno select new { s.SNO, c.CNO } ).Distinct()View Code
11.分组 过滤
实例 Code 查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。 select avg(degree) from score where cno like ‘3%‘ group by Cno having count(*)>=5 Linq: from s in Scores where s.CNO.StartsWith("3") group s by s.CNO into cc where cc.Count() >= 5 select cc.Average( c => c.DEGREE) Lambda: Scores.Where( s => s.CNO.StartsWith("3") ) .GroupBy( s => s.CNO ) .Where( cc => ( cc.Count() >= 5) ) .Select( cc => cc.Average( c => c.DEGREE) ) Linq: SqlMethod like也可以这样写: s.CNO.StartsWith("3") or SqlMethods.Like(s.CNO,"%3")View Code
12.分组
实例 Code 查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。 select avg(degree) from score where cno like ‘3%‘ group by Cno having count(*)>=5 Linq: from s in Scores where s.CNO.StartsWith("3") group s by s.CNO into cc where cc.Count() >= 5 select cc.Average( c => c.DEGREE) Lambda: Scores.Where( s => s.CNO.StartsWith("3") ) .GroupBy( s => s.CNO ) .Where( cc => ( cc.Count() >= 5) ) .Select( cc => cc.Average( c => c.DEGREE) ) Linq: SqlMethod like也可以这样写: s.CNO.StartsWith("3") or SqlMethods.Like(s.CNO,"%3")View Code
13. 多表查询
实例 Code select sc.sno,c.cname,sc.degree from course as c,score as sc where c.cno = sc.cno Linq: from c in Courses join sc in Scores on c.CNO equals sc.CNO select new { sc.SNO,c.CNAME,sc.DEGREE } Lambda: Courses.Join ( Scores, c => c.CNO, sc => sc.CNO, (c, sc) => new { SNO = sc.SNO, CNAME = c.CNAME, DEGREE = sc.DEGREE }) .Average()View Code
sql 、linq、lambda 查询语句的区别
标签:
本文系统来源:http://www.cnblogs.com/love201314/p/4767065.html
内容总结
以上是互联网集市为您收集整理的sql 、linq、lambda 查询语句的区别全部内容,希望文章能够帮你解决sql 、linq、lambda 查询语句的区别所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错,欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 gblab@vip.qq.com 举报,一经查实,本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。