Articles Cookbook
17 Aug 2017
Dorota Wdzięczna

An Illustrated Guide to the SQL OUTER JOIN

We’ve already discussed the SQL CROSS JOIN and INNER JOIN statements. It’s time to explore another: OUTER JOIN. What is it? How does it work? Let’s find out! If you’ve read our other posts, you know that you can link the data in two or more database tables using one of the many types of SQL join operator. Today, we’ll discuss the three kinds of OUTER JOIN: LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN.
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7 Aug 2017
Aldo Zelen

SQL Window Functions: Partitions and Ranking Functions

You’ve started your mastery of SQL window functions by learning RANK, NTILE, and other basic functions. In this article, we will explain how to use SQL partitions with ranking functions. Mastering SQL window functions (AKA analytical functions) is a bumpy road, but it helps to break the journey into logical stages that build on each other. In the previous Common SQL Functions article, you learned about the various rank functions, which are the most basic form of window functions.
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4 Aug 2017
Ignacio L. Bisso

SQL Window Function Example With Explanations

Interested in how window functions work? Scroll down to see our SQL window function example with definitive explanations! SQL window functions are a bit different; they compute their result based on a set of rowsrather than on a single row. In fact, the “window” in “window function” refers to that set of rows. Window functions are similar to aggregate functions, but there is one important difference. When we use aggregate functions with the GROUP BY clause, we “lose” the individual rows.
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31 Jul 2017
Marek Pankowski

How Recursive Common Table Expressions Work

Recursive Common Table Expressions are immensely useful when you're querying hierarchical data. Let's explore what makes them work. Common Table Expressions (CTEs) are some of the most useful constructions in SQL. Their main purpose is improving query design, which makes queries easier to read. One of the reasons CTEs are so popular is that they let you divide longer queries into shorter subqueries. These are easier to read and edit.
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24 Jul 2017
Dejan Sarka

High Performance Statistical Queries – Skewness and Kurtosis

In descriptive statistics, the first four population moments include center, spread, skewness, and kurtosis or peakedness of a distribution. In this article, I am explaining the third and fourth population moments, the skewness and the kurtosis, and how to calculate them. Mean uses the values on the first degree in the calculation; therefore, it is the first population moment. Standard deviation uses the squared values and is therefore the second population moment.
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20 Jul 2017
Dorota Wdzięczna

An Illustrated Guide to the SQL INNER JOIN

What is an SQL INNER JOIN, and how does it work? Let's find out! In my last article, I discussed the CROSS JOIN operation in SQL. Today, we'll look at INNER JOIN and how to use it. Is it the same as a JOIN? How many tables can you link with an INNER JOIN? These are all good questions. Let's look at the answers! What is an INNER JOIN?
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17 Jul 2017
Aldo Zelen

How to Use Rank Functions in SQL

Want to learn how to use ranking functions in SQL? They are a good choice if you want to start using SQL window functions! Learning about SQL window functions usually comes after you’ve built a foundation in the language, but these powerful functions take your skills up a level. As you master them, you’ll find better ways to solve query problems. When used for business intelligence applications, SQL queries combine data retrieval and advanced computations.
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11 Jul 2017
Dejan Sarka

Statistics in SQL: Measuring Spread of Distribution

Besides knowing the centers of a distribution in your data, you need to know how varied the observations are. In this article, we’ll explain how to find the spread of a distribution in SQL. Are you dealing with a very uniform or a very spread population? To really understand what the numbers are saying, you must know the answer to this question. In the second part of this series, we discussed how to calculate centers of distribution.
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7 Jul 2017
Dorota Wdzięczna

An Illustrated Guide to the SQL CROSS JOIN

What is an SQL CROSS JOIN statement? When should you use it? When shouldn't you use it? This post will tell you what you need to know about CROSS JOIN. You already know that you can use the SQL JOIN statement to join one or more tables that share a matching record. And if you're read the LearnSQL's post Learning SQL JOINs Using Real Life Situations, you know that there are many types of JOINs.
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6 Jul 2017
Francisco Claria

An Introduction to Using SQL Aggregate Functions with JOINs

Previously, we've discussed the use of SQL aggregate functions with the GROUP BY statement. Regular readers of the our blog will also remember our recent tutorial about JOINs. If you're a bit rusty on either subject, I encourage you to review them before continuing this article. That's because we will dig further into aggregate functions by pairing them with JOINs. This duo unleashes the full possibilities of SQL aggregate functions and allows us to perform computations on multiple tables in a single query.
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