select sClass 班级,count(*) 班级学生总人数, sum(case when sGender=0 then 1 else 0 end) 女生人数, sum(case when sGender=0 then 1 else 0 end)*1.0/count(*)女生所占比例, sum(case when sGender=1 then 1 else 0 end) 男生人数, sum(case when sGender=1 then 1 else 0 end)*1.0 /coun
本文继<Yarn源码分析之MRAppMaster上MapReduce作业处理总流程(一)>,接着讲述MapReduce作业在MRAppMaster上处理总流程,继上篇讲到作业初始化之后的作业启动,关于作业初始化主体流程的详细介绍,请参见<Yarn源码分析之MRAppMaster上MapReduce作业初始化解析>一文. (三)启动 作业的启动是通过MRAppMaster的startJobs()方法实现的,其代码如下: /** * This can be overridden to
The Suspects Time Limit: 1000MS Memory Limit: 20000K Total Submissions: 21586 Accepted: 10456 Description Severe acute respiratory syndrome (SARS), an atypical pneumonia of unknown aetiology, was recognized as a global threat in mid-March 2003. T
网上使用union all 查询记录总条数的参考资料比较少,所以记录下来,以便有同样需求的人使用. $rs_num = Db::query("select sum(a.b) as num from ( select count() as b from table1 where afrom = '".condition1."' UNION ALL select count() as b from table2 where afrom = '".condition2.&
step1:在mysql cmd中新建存储过程: drop procedure if exists queryCountByGrade ; delimiter // -- 定义存储过程结束符号为// create procedure queryCountByGrade(IN gradenameinput INT(),OUT counts ) begin select count(*) into counts from student where grade = gradenameinput;en
相同点:它们都以一张部门表(或类别表),其它表都有部门编号DepartmentID(类别编号) 案例一:一张表 select c.DepartmentID,c.DepartmentName, t.Num AS '人员数量' from T_Department as c left join (select DepartmentID,COUNT(*) AS Num from T_User group by DepartmentID) as t on c.DepartmentID= t.Depar