Articles Cookbook
14 Mar 2017
Marek Pankowski

Common SQL Job Interview Questions

Congratulations! Your SQL skills were strong enough to get you that job interview! Now, if you only knew what SQL questions and practical exercises a recruiter might ask you to do… This article is meant as a SQL practice for interviews. I’ll help you prepare for the SQL and database aspects of your job interview. Knowing SQL opens up opportunities in and out of IT, as this query language is used practically everywhere.
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21 Feb 2017
LearnSQL.com Team

The Complete Beginner’s Guide to SQL Fundamentals

If you're new to SQL, you've come to the right place. LearnSQL.com is a fantastic resource for learning SQL from the ground up. Before you start using SQL, it's helpful to understand what it is and how databases function. This guide provides a clear introduction to SQL fundamentals. At first, SQL may seem complex, but with the right approach, it becomes much easier to grasp. This guide will simplify the basics of SQL, making it accessible for beginners.
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25 Jan 2017
Jeffrey J. Keller

Grouping, Rolling, and Cubing Data

The first two articles in this series highlighted SQL Server's ability to organize data into user-defined windows and its aggregate functions. Part 3 will focus on other methods of aggregating and organizing data using built-in SQL Server features – specifically, its grouping functions. For consistency, the same base data will be used as in the first two parts of this series. CREATE TABLE WindowTable (WindowID INT IDENTITY, House Varchar(32), FullName Varchar(64), PhysicalSkill Decimal(4, 2), MentalSkill Decimal (4, 2)) GO
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24 Jan 2017
Maria Alcaraz

Performing Calculations on Date- and Time-Related Values

Relational databases support several date and time data types. In this article, we'll look at several arithmetic operations we can do on these types. These operations are logical and understandable, even for the beginning SQL coder. Let's first briefly explain the main data types used for dates and times. Keep in mind that data types may differ by database engine, so check your database documentation for specifics before you start working with them.
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3 Jan 2017
Aldo Zelen

How to Recognize SQL Text Data Type

How can you store textual information in database tables? Thanks to this post, you’ll learn the characteristics of every text data type in SQL Note: This post is intended for readers familiar with SQL data definition language (DDL) and the DDL CREATE statement. To learn more about DDL, check out LearnSQL.com. Most data types are classified as NUMERIC, CHARACTER, or DATE. In this post, we’re going to focus on each CHARACTER or text data type in SQL.
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28 Dec 2016
Aldo Zelen

Refine Results with SQL Set Operators

Using UNION, UNION ALL, EXCEPT, and INTERSECT to manage SQL query results. The function of SQL set operators is pretty simple; they allow us to combine results from different SQL queries into one result set. The best way to understand how set operators work is to use visual methods like the Venn diagram. For those of you not familiar with Venn diagrams, they are two circles that represent items or collections of items.
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20 Dec 2016
Adrian Dembek

6 Common SQL Syntax Mistakes All Learners Make

We all make mistakes when learning a new language – especially at the beginning. New words, complicated grammar... Everyone needs time to master a language. But when we get immediate feedback, we can progress more quickly. The same goes for learning SQL. In this article, we'll look at 6 common SQL syntax mistakes most SQL learners make. Learning SQL can feel like deciphering a complex code, especially when you’re just starting out.
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19 Dec 2016
Marcos Pierri

8 Tips Absolute Beginners Can Use to Fix SQL Queries

Code errors are common – and frustrating. And when you're just learning SQL, it can be very challenging to find and fix your mistakes. In this post, we'll show you eight ways to solve or eliminate common SQL coding errors. Today, we'll talk about some tips the SQL beginner can use to avoid several common errors. These tips work in any database environment. As we go along, we'll be showing some error messages.
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13 Dec 2016
Aldo Zelen

How to Learn SQL: 6 Ideas for Newbies

Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, there are a lot of options you can use to learn SQL online, offering the convenience and flexibility to learn at your own pace and in your own environment! But we then come to a new roadblock. Where to begin?
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13 Dec 2016
Maria Alcaraz

Correlated Subquery in SQL: A Beginner’s Guide

Sometimes, using a SQL correlated subquery is the only way to solve a statement. But these subqueries can be very slow. In this post, we’ll talk about when to use a correlated subquery, why, and how to do it. Subqueries are an important resource for increasing the expressive power of SQL. Subqueries are simply a SELECT statement inside another SELECT. We can use them in different places inside a SELECT, such as in the WHERE, HAVING, or FROM clauses.
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