SQL Statement Syntax AND / OR SELECT column_name(s)FROM table_nameWHERE conditionAND|OR condition ALTER TABLE ALTER TABLE table_name ADD column_name datatype or ALTER TABLE table_name DROP COLUMN column_name AS (alias) SELECT column_name AS column_al…

C++ string 用法详解 字符串分割(C++)  C++ QUICK REFERENCE Matt Mahoney, mmahoney@cs.fit.edu DECLARATIONS enum weekend {SAT,SUN};   // weekend is a type with values SAT and SUN enum weekend day;         // day is a variable of type weekend enum weekend {SAT=0,S…

问题 datafrme提供了强大的JOIN操作,但是在操作的时候,经常发现会碰到重复列的问题.在你不注意的时候,去用相关列做其他操作的时候,就会出现问题! 假如这两个字段同时存在,那么就会报错,如下:org.apache.spark.sql.AnalysisException: Reference 'key2' is ambiguous 实例 1.创建两个df演示实例 val df = sc.parallelize(Array( ("yuwen", "zhangsan&quo…

C# C# Cheatsheet & Notes Coding Guidelines for C# 3.0, 4.0, 5.0 Core C# and .NET Quick Reference C# Basics Reference Sheet C C Reference Card (ANSI) Objective-C Cheatsheet & Quick Reference C Cheat Sheet by Jill Crisman C++ C++11 Regex Cheatsheet…

ASP.NET Web Pages (Razor) API Quick Reference By Tom FitzMacken|February 10, 2014 Print This page contains a list with brief examples of the most commonly used objects, properties, and methods for programming ASP.NET Web Pages with Razor syntax. Desc…

mongo Shell Command History You can retrieve previous commands issued in the mongo shell with the up and down arrow keys. Command history is stored in ~/.dbshell file. See .dbshell for more information. Command Line Options The mongo shell can be sta…

General \copyright show PostgreSQL usage and distribution terms \g [FILE] or ; execute query (and send results to file or |pipe) \h [NAME] help on syntax of SQL commands, * for all commands \q quit psql Query Buffer \e [FILE] edit the query buffer (o…

1.关心你的技艺 Care About Your Craft 如果不在乎能否漂亮地开发出软件,你又为何要耗费生命去开发软件呢? 2.思考!你的工作 Think! About Your Work 关掉自动驾驶仪,接管操作.不断的批评和评估你的工作. 3.提供各种选择,不要找蹩脚的借口 Provide Options,Don't Make Lame Excuses 要提供各种选择,而不是找借口.不要说事情做不到:说明能够做什么. 4.不要容忍破窗户 Don't Live with Broken Wi…

Basic basic.ack(delivery-tag delivery-tag, bit multiple)Support: fullAcknowledge one or more messages.Acknowledge一个或多个message When sent by the client, this method acknowledges one or more messages delivered via the Deliver or Get-Ok methods. When sen…

参考: http://eigen.tuxfamily.org/dox/AsciiQuickReference.txt // A simple quickref for Eigen. Add anything that's missing. // Main author: Keir Mierle #include <Eigen/Dense> Matrix<, > A; // Fixed rows and cols. Same as Matrix3d. Matrix<, Dyna…

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pdf文件:https://files.cnblogs.com/files/MakeView660/JavaScript_Quick_Reference_Card.pdf…

近段时间,接触正则较多,常规法则如下,网摘内容,方便查阅.…

推荐一个小插件,SQL Prompt,配合Microsoft SQL Server Management Studio,使用起来非常方便,同时再加上以下几个快捷键: (1)ctrl+5或F5,运行代码,如果想运行特定的语句,那么只是选中该语句,然后F5或ctrl+E即可. (2)ctrl+L:显示执行计划. (3)ctrl+R:显示隐藏下面的结果窗口,增大自己书写sql的空间. (4)ctrl+K,然后按Y,格式化SQL代码. 此随笔或为自己所写.或为转载于网络.仅用于个人收集及备忘. 官方:Q…

SQL to Aggregation Mapping Chart https://docs.mongodb.com/manual/reference/sql-aggregation-comparison/ On this page Examples Additional Resources The aggregation pipeline allows MongoDB to provide native aggregation capabilities that corresponds to m…

1. Introduction 1.1. About 1.2. Sphinx features 1.3. Where to get Sphinx 1.4. License 1.5. Credits 1.6. History 2. Installation 2.1. Supported systems 2.2. Compiling Sphinx from source 2.2.1. Required tools 2.2.2. Compiling on Linux 2.2.3. Known comp…

Learn SQL Reporting on Windows Azure (9-Step Tutorial) 4 out of 4 rated this helpful - Rate this topic Learn how to create and deploy SQL reports on Windows Azure using Report Builder andAdventure Works for Azure sample data. Each step is clearly mar…

here were various changes to memory related DMVs, DBCC memory status, and Perfmon counters in SQL Server 2012 as part of the redesign of the Memory Manager component of SQLOS. The Memory Manager redesign resulted in being able to more accurately size…

前言 当我们利用EF这个ORM框架时,我们可能会利用LINQ或者原生的SQL语句来进行数据操作,此时我们无法确定我们的代码是否会给数据库带来一定的负载,当给数据库带来一定的压力时,由于项目中对数据进行相应的操作实在是太多,我们无法准确的去进行定位,又或者我们不是专业的DBA,无法准确的去分析SQL性能的优劣,此时该怎么办呢?我们完全不需要DBA,我们可以通过相应的操作来判断一段SQL代码的好坏,这就是我们本节需要讲的内容,利用EF中监听者来判断SQL性能,在之前系列中也有提到,可以参考之前系列.…

转自:http://www.sqlusa.com/bestpractices/training/scripts/dynamicsql/ Dynamic SQL & Stored Procedure Usage in T-SQL Important security article related to dynamic SQL: How To: Protect From SQL Injection in ASP.NET ------------ -- Dynamic SQL QUICK SYNTA…

This article gives you all the information you need in order to begin working with numbers in your PL/SQL programs. Numbers in PL/SQL PL/SQL offers a variety of numeric datatypes to suit different purposes: NUMBER. A true decimal datatype that is ide…

参考:Apache Impala Guide--Impala SQL Language Reference. Impala使用和Hive一样的元数据存储,Impala可以访问使用原生Impala CREATE TABLE创建的表和Hive DDL创建的表: Impala支持和HiveQL类似的DML: 支持TRUNCATE(至少在5.5及之前,不支持Kudu表) UPDATE/UPSERT(5.10开始支持Kudu表) Impala提供了很多和HiveQL等价的内置函数: 支持大多数子句如WIT…

一. Bulk 概述 本来只想测试一下Bulk Collect 和update性能的,但发现Bulk 的东西还是很多的,在OTN上搜了一些,整理如下. 1.1 Bulk Binding 和 Bulk SQL From:  http://download.oracle.com/docs/cd/E11882_01/appdev.112/e17125/adfns_packages.htm#ADFNS343 Oracle Database uses two engines to run PL/SQL b…

前言 DDL(Data Definition Language)语句:数据定义语句,这些语句定义了不同的数据段.数据库.表.列.索引等数据库对象.常用的语句关键字主要包括 create.drop.alter 等. 1.DDL 数据库操作语句 1)创建数据库语句 # 创建数据库,数据使用默认编码方式 utf8mb4 # create database 数据库名; > create database test; Query OK, 1 row affected (0.04 sec) # 创建数据库,…

➪SQL ➪基本类型 char / varchar / int / smallint / numeric / real, double precision / float ➪数据定义 create table department//定义SQL关系 (dept_name varchar(20),//属性名 域 building varchar(15), budget numeric(12,2), primary key(dept_name));//完整性约束 primary key, forei…

java 触发器 包 你可以编写用户定义的函数(用pl/sql,java,c)来提供在sql中或sql内置函数中不可用的功能 有时,我们会发现有些功能通过PL/SQL完成会很麻烦,而通过C/C++语言编程则会容易很多.因此,oracle提供了在PL/SQL程序里直接调用外部函数(包括C函数或Java方法)的功能,从而扩展了PL/SQL的程序功能. 在Oracle的存储过程和函数中,其实IS和AS是同义词,没有什么区别.还有在自定义类型(TPYE)和包(PACKAGE)时,使用IS和AS也并没有什…

JavaScript Reference for Microsoft Dynamics CRM 2011 / 2013 98 Replies Here’s a quick reference guide covering Microsoft CRM syntax for common jscript requirements. Most of the examples are provided as functions that you can easily test in the OnLoad…

此文章来自官方文档,说明了,对于不支持pg 标准的sql 查询的变通方法,实际使用的时候有很大的指导意义 As Citus provides distributed functionality by extending PostgreSQL, it is compatible with PostgreSQL constructs. This means that users can use the tools and features that come with the rich and ex…

https://blog.csdn.net/lukeUnique/article/details/79331779 https://mauro-pagano.com/2014/10/27/when-the-going-gets-tough-the-tough-get-going-aka-sqlt-xplore/ When upgrading a database sometime you find that one or more SQLs run slower because of a new…

Note to the Reader - Docs Being Revised for Selenium 2.0! Introduction Test Automation for Web Applications To Automate or Not to Automate? Introducing Selenium Brief History of The Selenium Project Selenium’s Tool Suite Choosing Your Selenium Tool S…