Top 10 SQL Window Functions Interview Questions by Ignacio L. Bisso 16 Jul 2021 Many interesting job positions require SQL skills – and that includes window functions, which are not commonly taught in online courses. In this article, I will cover the top window function questions for every experience level. If you’re going for a job interview for an advanced SQL position or for intermediate to advanced data analyst positions, you’ll probably be asked about your knowledge of SQL window functions. Don’t panic! Although these functions aren’t commonly covered in online courses, we’ve got the answers right here. Read more How to Compute Year-Over-Year Differences in SQL by Ignacio L. Bisso 26 May 2021 How did your business do this year compared to last year? The year before? Find out how to use SQL to calculate year to year and month to month differences. Year-over-year (YOY) comparisons are a popular and effective way to evaluate the performance of several kinds of organizations. Year to year differences are easy to understand – e.g. it’s easy to understand that your revenue growth is 35% year to year. Read more Why Do You Need a Primary Key in a Database Table? by Ignacio L. Bisso 29 Apr 2021 What is a primary key and why is it so important in SQL? Find out in this article. Primary keys are a central element in SQL databases. They provide a unique value that can identify a specific row in a table, which opens up a lot of other benefits. This article covers what a primary key is, how it works, and how to use it in an SQL database. Read more What Is a NOT NULL Constraint in SQL? by Ignacio L. Bisso 24 Mar 2021 SQL has several ways of dealing with NULLs. In this article, we’ll focus on the NOT NULL constraint and other NULL-related clauses. Understand this and you’ll take an important step in your SQL growth! Before we get straight into the NOT NULL constraint, let’s quickly define what NULLs and constraints are. NULL values are a central concept in SQL databases. The idea behind a NULL value is simple: a NULL value means that we do not have a known value for that field. Read more Data Types in SQL by Ignacio L. Bisso 29 Jan 2021 Read this article and learn the ABC of SQL data types. Data types are used to define the type of data stored in a database. However, there are related concepts that a good SQL developer should know: data type conversion, what operations are possible between different data types, date arithmetic, etc. SQL also provides functions that manipulate values of different data types (i.e. functions for string data, date and time data, etc. Read more What Is a Database Index? by Ignacio L. Bisso 25 Dec 2020 Database indexes are critical to query speed and efficiency. Learn when, why, and how to use them – and when not to – in this post. Indexes are very important database objects; they optimize data access and improve database performance by helping the database execute SQL queries faster. Why not take this opportunity to learn how indexes work and how to create them? What Is a Database Index? Indexes are data structures that can increase a database’s efficiency in accessing tables. Read more What Is a Foreign Key in SQL? by Ignacio L. Bisso 27 Nov 2020 What does a foreign key do in SQL? Why would you need one? Learn the ABCs of foreign keys in five minutes. Foreign keys are a central concept in SQL databases; they allow us to enforce data consistency. Usually they work with primary keys to connect two database tables, like a virtual bridge. All SQL developers need to know what SQL foreign keys are, how they work, what data values are allowed in them, and how they’re created. Read more What is a Primary Key in SQL? by Ignacio L. Bisso 22 Oct 2020 Primary keys are an important concept in SQL databases. They provide a unique ID for every row in a database table. As an SQL developer, you should know what primary keys are, what data values are allowed in them, and how to create them. Read this article to learn the ABCs of primary keys in 10 minutes. How to Identify Rows in a Table Tables are the main objects in an SQL database, and as you probably know, tables store records or rows. Read more What Is the MySQL OVER Clause? by Ignacio L. Bisso 24 Sep 2020 If you want to learn window functions in MySQL, you need to understand the OVER clause. In this article, we use real-world examples to explain what the MySQL OVER clause is, how it works, and why it’s so awesome. In 2018, MySQL introduced a new feature: window functions, which are accessed via the OVER clause. Window functions are a super powerful resource available in almost all SQL databases. They perform a specific calculation (e. Read more How Does SQL GROUP BY Work? by Ignacio L. Bisso 27 Aug 2020 Grouping results is a powerful SQL feature that allows you to compute key statistics for a group of records. GROUP BY is one of SQL’s most powerful clauses. It allows you to see data in a new way and find key metrics (like the average, maximal, and minimal values in a group of records). Without GROUP BY, all the results we obtain are oriented to records. With GROUP BY, we can create groups of records and calculate metrics on each group. Read more «« « 1 2 3 4 » »»