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Tags: Document learning ges DDR Select RES data varchar TPS1. Select the database you want to use (select the test database created in the previous article) The existing database Mysql>use test; Select the test database; 2. Create a table 2.1column represents the name of each column, datatype represents the data type of each column (available data type: https://www.w3schools.com/sql/sql_datatypes.asp) 2.2 Creating a Table Mysql> CREATE TABLE Persons (-PersonID int,LastName varchar (255),Firs

A CHECK1.Check constraints are used to limit the range of data that is filled inWhen a check is used on a column in a table, it restricts only the data for that columnWhen check is used for a table2. Syntax: MySQL1. Use check (constraints) directly when creating a table2. Add a check to a table you've created2.1 Single condition　　More than 2.2 conditions　　3. Discard CHECK constraints(vi) MySQL: Learn SQL syntax (check constraints) on W3Schools documen

)3.4FOREIGN key (foreign key)------used to mark a row of this table in another table or this table3.5CHECK------Ensure that a column of data meets a particular condition3.6The default------sets an initial value that is set to this value when the data is not assigned3.7INDEX------used to quickly create and retrieve data from a database4. This is a constraint summary, I'll try these constraints later, (not full,unique,primary key has been tried in the blog that added the primary key)(attached) MyS

[Solid Ruby Basics] Ruby Quick Start, solid ruby Quick Start Address: http://www.cnblogs.com/aiweixiao/p/6664301.html Document outline Scan the public account1. Ruby Installation 1.1) [install Ruby] Ruby installation on Linux/Un

Keywords: Ruby on Rails, instantrails, windows, getting started, tutorial I always wanted to try Ruby on Rails, but I was not familiar with Apache and MySQL, and I was not confident in setting up the rails environment. So I never started. After learning about instantrails, finally, we set up the Ruby on Rails Development Environment on Windows and started learni

Demonstrate Ruby's six characteristics that are easy to be misunderstood with actual code. The Code demonstrates ruby misunderstanding. Introduction: if you are a C ++ developer, you need to use Ruby to quickly execute some prototype designs. When you pick up a Ruby reference book (such as Pickaxe) or browse a Ruby web

Add fire to Ruby: Ruby will become popular again Ruby, which is widely regarded as a web language, has always been very popular, but it will become more popular now. AltRubies pushed Ruby to a level we never imagined. Is Ruby the preferred choice for browsers, mobile apps,

Tutorial on system management by writing scripts in Ruby, and ruby System Management Introduction Ruby is an extremely rich, free, simple, scalable, portable, and object-oriented scripting language. Recently, it is widely used in the Web field. To a certain extent, this is attributed to the very powerful Web application development framework Rails, Which is exact

Ruby on Rails Session 1: How to Build a Ruby on Rails on the Ubuntu., railsubuntuAbout Ruby on Rails Ruby on Rails is an application stack that provides developers with a framework to quickly create a variety of web applications. ruby on Rails does take a little while to ins

The tailor made for the Basix users among. If you've been itching to try out Ruby and/or Rails, if the Terminal are somewhat new to you, your may find that even the PR Ocess of installing it can generate countless confusing errors. This article would detail the exact steps you need to follow for get Ruby up and running on your Mac. Step 1-RVMWhat are interested to know are that

Detailed tutorial on connecting to the database in Ruby program, ruby Database This section describes how to use Ruby to access databases. The Ruby DBI module provides database-independent interfaces similar to the Perl DBI module for Ruby scripts. DBI is the Database indepe

Further dive into the class and object concepts in Ruby and the concept of ruby objects Ruby is a pure object-oriented language, and all projects seem to need Ruby as an object. Every value in Ruby is an object, even the most primitive: String, number or even true or false.

Detailed explanation of the iterator IN Ruby and the Ruby Generator D guago recently wanted to build a website. In addition, he had long had the idea of learning a dynamic language. Among the programming languages that meet two conditions, Ruby and Python are the most appropriate. Now Ruby on Rails is booming! Therefor

Understand Ruby scopes and Ruby scopes What is scope? When talking about the scope, you should immediately thinkVariableAndVisibilityThese two words,VariableAndVisibilityIt is the main content of the scope. Yes, the scope is about where the code variables are visible. After you fully understand the scope, I will give you a piece of code, you can easily know what variables are visible at this time, and most

The concept of class objects in Ruby and the concept of ruby objects Object-oriented Programs involve classes and objects. A class is a blueprint created from an individual object. In object-oriented terms, we say that James's bicycle is an object instance called a bicycle. Example of any vehicle. It includes wheel, horsepower, fuel or gas tank capacity. Data members of vehicles with these features. These f

Ruby implements two mail sending methods, and ruby implements mail sending. In fact, as long as you are willful, you can use telnet to send emails. However, this cat is not so capricious. We should use the KISS Principle to send emails. This blog post only describes how to send emails, but does not involve email receiving. If you have the opportunity to open a separate blog post in the future.

1. Why Ruby? Why do many Java developers focus on Ruby? Ruby is a general-purpose scripting language created in Japan 10 years ago. It is a pure object-oriented language. Unlike Java, everything in ruby is an object. Ruby syntax mainly comes from smalltalk, Python and Ada.

Ruby basic syntax getting started tutorial, ruby basic syntax tutorial Let's write a simple Ruby program. All Ruby file extensions are. rb. Therefore, put the following source code in the test. rb file.Instance #!/usr/bin/ruby -wputs "Hello,

Most Ruby programs, their design, logic, and action, are all centered around objects. The main task of writing a Ruby program is to create objects and then give them the ability to perform actions. Ruby is an OOP language, an object-oriented language in which you perform calculations, data processing, input, and output by creating objects and then letting the ob

About Ruby on Rails Ruby on Rails is an application stack that provides developers with a framework to quickly create a variety of Web applications. ruby on Rails does take a little while to install on a virtual server, but luckily there are a lot of helpful tools to make this process as easy as possible. you can run this tutorial on your droplet as a user with S