The XML file format for Vertabelo has changed to version 2.3. Read this article to find out what is new. Vertabelo keeps its models in XML format; if you need, you can download the files and extract information from them. Previously, we used XML version 2.1, as discussed in this article . We’ve switched to XML 2.3, and a couple of changes took place. These changesmake no difference for most Vertabelo users
Did you know that you can embed your database model in your website? If you haven’t tried this yet, now’s your chance – we’ve recently improved the process. It’s an excellent way to share ideas with readers or make projects available to co-workers.You might have already seen some interactive models embedded in our blog. They look like this:If you want to find out how to embed your own model on a website, follow these steps.
In an earlier article on data modeling we promised to give you a set of exercises to practice finding entities and attributes. Here is the second installment of our problem set. Enjoy.Problem 1: CountriesDescription:Find the right entities and their attributes to represent all the countries in the world, their interior regions (which can be called states, provinces, or regions) and their cities. We want to represent each country’s name, continent, date of independence, type of government and population. For each region (or province, state, etc.) we wish to store the capital city, the name of the governor, and the population. Finally, for each city we want to have the name, founding date, population, and the number of schools per inhabitant. We would also like to represent what every country calls its interior regions.
In an earlier article on data modeling we promised to give you a set of exercises to practice finding entities. Well, here they are. Have fun!Problem 1: Language SchoolMr. Trotter, the proprietor of a rapidly-growing language school, wants to introduce a new system in his company. He can no longer keep track of all the information on his own, so he’s asked for our help. He is a bit chaotic, though. This is what he said:
You’re finally ready to get down to real data modeling. We’ll start off with entities and their attributes. Entities are the basic building block of every data model. In this post, you’ll find out what they are and how to identify them.What Is an Entity? What is a Specific Instance of an Entity?Data models help us to identify what kind of information we’ll store in our system. We use such models to address the question
The General Availability version of MySQL is still version 5.6, but the development release of MySQL 5.7 definitely introduces some exciting changes to the world of database management systems. Is it worth giving a try? In this article, we’ll have a closer look at a few brand-new features that may help you decide to do so.Native JSON SupportJSON (short for Java Script Object Notation) is a format for storing information which can be a good alternative to XML. If you haven’t encountered it already, take a look at a very simple example of a JSON document:
Data modeling is an essential step in the process of creating any complex software. It helps developers understand the domain and organize their work accordingly. In this article, which begins a new series devoted to database modeling, we’ll try to convince you why you should include it in your projects and what it looks like.Do I Really Need Data Modeling?As a novice developer, you often start your programming adventure withsimpleapplications like the sieve of Eratosthenes or enumerating the Fibonacci sequence. In such cases, a data model is not required – these programs are quite simple and they have a clearly defined input and clearly defined output. The difficulty of these tasks lies in the algorithm which has to work correctly and quickly. The data themselves are easy to understand: you provide some parameters and you get a set of numbers as a result.
The SQL Language seems easy to learn – the commands follow a simple syntax and don’t describe the specific algorithms used to retrieve data. The simplicity might, however, be deceptive. Not all the database functions operate with the same efficiency. Two very similar queries can vary significantly in terms of the computation time. This article presents some of the best practices that can greatly boost your SQL queries.1. Learn How to Create Indexes Properly
Execution plans can become a very useful tool for every database developer. They provide a deeper understanding of the mechanisms applied in the processing of queries. This article will take a closer look at how execution plans are retrieved and how to read them.What Are Execution Plans?SQL is, to a great extent, a declarative language. The user defineswhatshould be done but does not specifyhowthe queries should be executed. There are many ways in which certain parts of an SQL statement can be processed. For example, predicates can be computed in any sequence and subqueries can be turned into joins if necessary.
Generating unique integers is a very common task in database systems. Many applications require each row in a given table to hold a unique value. One way to tackle this problem is to use sequences.What are Sequences?A sequence is a database object which allows users to generate unique integer values. The sequence is incremented every time a sequence number is generated. The incrementation occurs even if the transaction rolls back, which may result in gaps between numbers. Similarly, gaps may arise when two users increment the same sequence concurrently.