在使用sql语句时,很多人都会分不清order by与group by,其实简单的说: order by -- 排序 group by --分组 1.order by是行的排序,默认为升序. 有两种方式,ASC升序.降序DESC. 其后面必须列出排序的字段名,当然可以是多个字段名. 下面通过例子来看下它的简单用法: 数据库中有一张Apartment表,其表中的字段值如下: 要求:将表中数据按Number列降序排列 /*Apartment为表名*/ select * from Apartment
In geology, a river system can be represented as a directed graph. Each river segment is an edge; with the edge pointing the same way the water flows. Nodes are either the source of a river segment (for example, a lake or spring), where river segment
我在一个业务中采用了按月的分表策略,当查询的条件跨月的时候,使用了union all汇总2个表的数据,并按插入时间倒序排列.查询并不复杂,但是当执行的时候却报错了. SELECT * FROM `table_201604` ORDER BY `REPORT_TIME` DESC UNION ALL SELECT * FROM `table_201605` ORDER BY `REPORT_TIME` DESC [Err] 1221 - Incorrect usage of UNION and O
基数排序 package basic.sort; import java.util.Arrays; import java.util.Random; public class RadixSort { /** * use LSD * @param number * @param d key code number in fact is the radix; */ private void radixSort(int[] number, int d) { int k = 0; int n = 1;
Program.cs class Program { static void Main(string[] args) { NoMethodLogging(); Console.WriteLine("Press any key to continue..."); Console.ReadLine(); SimpleMethodLogging(); Console.WriteLine("Press any key to continue..."); Console.Re
Django的form表单一般具有两种功能 1. 验证输入 2.输入HTML ---------模板----------- from django import forms class BookForm(forms.Form): name = forms.CharField(max_length=10) publish_date = forms.DateField() -------视图----------- def forms(request): Forms = form_models.Boo
默认的sp_helptext 如果存储过程每行代码太长会自动截断 把这个sp_helptextplus添加到SSMS的keyboard快捷键里面 SET QUOTED_IDENTIFIER ON SET ANSI_NULLS ON GO CREATE PROC sp_HelpTextPlus @SPNAME NVARCHAR(255) AS BEGIN DECLARE @objname NVARCHAR(776) = @SPNAME; DECLARE @ObjectText NVARCHAR(M
一些联合表查询语句,这些表里都建立有索引.在没有加 option ( force order ) 前,整个查询费时40多秒,但 单独表 查询基本不到1秒.查看查询计划后发现查询过程是从table n开始使用索引与 table s 等匹配,再与table m中的b匹配,导致整个查询最多表的扫描次数上千次多,逻辑读上万次.加了 option ( force order ) 后,最多表查询扫描次数在10次以内,逻辑读最多的也就千出头.整个查询费时不到1秒,CPU运行占用时间599MS.分享一下. 以下
Sum It Up Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 3538 Accepted Submission(s): 1788 Problem Description Given a specified total t and a list of n integers, find all distinct sums usin