Articles Cookbook
26 May 2020
Rebecca McKeown

Is it Difficult to Learn SQL?

It’s the number one question asked by the students of SQL and those new to the IT world. Is it difficult to learn SQL? If you came here because you’ve been pondering that very same question, take some comfort in the fact that in no way are you alone. Even the idea of SQL can be intimidating to those of us without a tech background, but it doesn’t have to be that way.
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22 May 2020
Kamil Bladoszewski

Subquery vs. CTE: A SQL Primer

Have you ever wondered about the differences between a subquery and a common table expression (CTE) in SQL? The concepts seem very similar, but knowing the difference – and when to use each one – will help you write efficient and readable queries. First, we’ll explain the concepts underlying subqueries and CTEs. Then we’ll look at a few examples and finally analyze the pros and cons of each technique.
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21 May 2020
Ignacio L. Bisso

How to Number Rows in an SQL Result Set

Have you ever needed to add a sequential number to the records in the result of an SQL query? It’s not as simple as it looks! Find out how to do it correctly in this article. To number rows in a result set, you have to use an SQL window function called ROW_NUMBER(). This function assigns a sequential integer number to each result row. However, it can also be used to number records in different ways, such as by subsets.
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19 May 2020
Jakub Romanowski

Major Companies Using PostgreSQL: Purposes & Examples

Which companies use the open-source relational database management system PostgreSQL? Find out … and learn why you should be a PostgreSQL user too. You know the blue elephant logo. You have heard that PostgreSQL is a very good solution. But which companies use it? Here is a list of the largest IT and business companies that use PostgreSQL (or Postgres, for short). Multinationals worth billions of dollars can't be wrong, right?
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15 May 2020
Dorota Wdzięczna

Overview of Ranking Functions in SQL

SQL ranking functions make working with relational databases easier, especially for data analysts, marketers, and financial specialists. These functions are used to assign a ranking number for each record and allow you to efficiently create useful reports. SQL ranking functions are window functions. Window functions compute the result based on a set of rows. The word “window” refers to this set of rows. Let’s look at the syntax of ranking functions:
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14 May 2020
Ignacio L. Bisso

Beginner’s Guide to the SQL Subquery

Subqueries are a powerful SQL resource, allowing us to combine data from multiple tables in a single query. In this article, we’ll teach you everything you need to begin using subqueries. Perhaps the simplest definition of a SQL subquery is “A query inside a query”. Subqueries are so easy to understand that they often appear in the opening chapters of SQL courses. However, there are many variants of subqueries that need to be explained.
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13 May 2020
Tihomir Babic

11 Advanced SQL Interview Questions (and Answers)

Do you want to move to a job that uses SQL? Are you unsure about what to expect during the job interview or how to benchmark your knowledge? This article will give you a good idea of where you stand. If you feel stuck in your job, you’re not the only one. The modern division of work pushes people to perform very specific tasks, expecting them not to look at what's on the other side.
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12 May 2020
Adrian Więch

SQL in Google Sheets? Yes, We Can!

Did you know that you can write SQL-like queries in Google spreadsheets? This feature is incredibly powerful, versatile, and can replace most of the functionalities offered by Excel’s pivot tables. Read our article to find out how you can easily use the QUERY function to efficiently work with your Google Sheets data. Relational databases share many features with spreadsheets. When we explain what databases are, we often say that they are a bit like spreadsheets except they give us more control over larger amounts of data.
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8 May 2020
Marija Ilic

Why Should I Learn SQL Window Functions?

SQL has been around for more than 25 years. Its basic syntax – like SELECT, WHERE, GROUP BY, HAVING, and ORDER BY – is well known. But is there something besides traditional SQL? Can you go beyond the basics and improve your skills? The answer to this question is yes. There is a modern version of SQL. In this article, we are going to dive into the modern version and learn about SQL window functions.
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7 May 2020
Kateryna Koidan

What Is a Nested Query in SQL?

Have you ever wished that you could build a query with several SELECT statements? Good news! You can do this – and a lot more – with SQL’s nested queries. Nested queries are an essential part of writing efficient SQL code. If you’ve been learning SQL and writing queries, you’ve likely faced situations where you need to put a SELECT statement inside another SELECT statement. You might wonder, "Can I really do that in SQL?
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