Articles Cookbook
4 May 2017
Marek Pankowski

Book Review: “Learn SQL the Hard Way” by Zed A. Shaw

“Learn SQL the Hard Way” by Zed A. Shaw is a great ebook for those who want to learn SQL essentials. At $19.99 USD, it may seem a bit expensive for an ebook, but you’re getting a DRM-free PDF, plus a whole bunch of explanatory videos and additional files. Who should read “Learn SQL the Hard Way”? Anyone interested in SQL basics – modifying databases or selecting information. Make no mistake about it: this book focuses heavily on the practical side of database language.
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27 Apr 2017
Maria Alcaraz

NULL Values and the GROUP BY Clause

We've already covered how to use the GROUP BY clause and some aggregation functions like SUM(), AVG(), MAX(), MIN(), COUNT(). In this article, we will explain how the GROUP BY clause works when NULL values are involved. We will also explain about using NULLs with the ORDER BY clause. The best way to master GROUP BY and NULL in SQL is through practice. I recommend the SQL Practice track at LearnSQL.
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20 Apr 2017
Dorota Wdzięczna

How to Use LIKE in SQL: SQL Pattern Matching

SQL pattern matching is a very important and useful ability. In this article, we look at how you can perform it using LIKE in SQL. SQL Pattern matching is a very simple concept. It allows you to search strings and substrings and find certain characters or groups of characters. Apart from SQL, this operation can be performed in many other programming languages. In this article, we’ll examine how you can use LIKE in SQL to search substrings.
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18 Apr 2017
Aldo Zelen

Understanding Numerical Data Types in SQL

Working with databases of any kind means working with data. This data can take a couple of predefined formats. As you start on your learning path with LearnSQL.com, you will start to understand SQL's different data types. In this article, we will cover different variations of the SQL numeric data type. We'll also examine some functions that convert data from one type to another. Creating tables is the first step in any SQL coding project.
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13 Apr 2017
Marek Pankowski

5 SQL Functions for Manipulating Strings

SQL functions used for manipulating strings, commonly called string functions, are among most important SQL’s tools. In this post, we’ll look at five ways you can perform various operations on strings. There are many SQL functions that let you “edit” string data. As you learn SQL, you’ll see how useful they prove. Some sql trim off unneeded spaces or characters; others tell you how long a string is. These functions give you a lot of opportunities to transform and work with strings, which makes your code more effective.
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10 Apr 2017
Francisco Claria

Preventing Common SQL Mistakes

Regardless of the engine you are using (SQL Server, MySQL, Oracle, etc.), you can prevent common errors and simplify the debugging process. This article will discuss some of the common SQL mistakes you’ll face and will help you correct them easily. One of the best ways to prevent the most common SQL mistakes is to keep your queries clear and readable. It’s very easy to forget the ideas behind your code!
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4 Apr 2017
Aldo Zelen

5 Books That Will Grow Your SQL Skills

Looking to take your database skills up a notch? I've spent some time digging into various resources, and I want to share five advanced SQL books that really stood out. These texts are not just about learning the basics: they're about mastering the intricacies of SQL and truly enhancing your database management prowess. Whether you're troubleshooting complex queries or optimizing performance, these books provide insights that are both practical and transformative.
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30 Mar 2017
Marek Pankowski

How to Organize SQL Queries When They Get Long

The first long SQL query you’ll have to deal with is likely to be hard for you to structure and understand. These five tips will teach you the best way to organize SQL queries, i.e. write and format them. As we all know, SQL queries are essential to database management. Without them, it would be extremely difficult to find and work with the information in a database. Query length depends on the type of information we need and the size of the database.
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28 Mar 2017
Dejan Sarka

Statistics in SQL: Calculating Frequencies & Histograms

Database and Business Intelligence (BI) developers create huge numbers of reports on a daily basis, and data analyses are an integral part of them. If you wonder whether you can perform statistical analysis in SQL, the answer is ‘yes’. Read my article to learn how to do this! Statistics are very useful as an initial stage of a more in-depth analysis, i.e. for data overview and data quality assessment. However, SQL statistical analysis possibilities are somewhat limited as there are not many statistical functions in SQL Server.
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22 Mar 2017
Marian Dziubiak

Improving Query Readability with Common Table Expressions

What is a Common Table Expression, or CTE? Where do you use them, and why? This post answers your questions. Simply put, Common Table Expressions (also known as WITH clauses) are essentially named subqueries. They also provide additional features like recursion. If you're new to subqueries, I recommend you read the SQL Subqueries article before continuing. The main purpose of Common Table Expressions is to improve the design and readability of an SQL statement.
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