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24 Jul 2017
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.
20 Jul 2017
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?
17 Jul 2017
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.
11 Jul 2017
SQL Statistical Analysis Part 3: 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.
7 Jul 2017
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.
6 Jul 2017
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.
26 Jun 2017
A Beginner’s Guide to SQL Aggregate Functions
Aggregate functions are powerful SQL tools that compute numerical calculations on data, allowing the query to return summarized information about a given column or result set. These functions can be used in conjunction with the GROUP BY statement. Let’s see how they work using some easy examples. SQL Aggregate Functions Suppose we have users residing in a city, and we store their information in two tables. These tables and their relationship are shown below:
23 Jun 2017
Introducing SQL Set Operators: Union, Union All, Minus, and Intersect
Ever heard terms such as union and intersection in SQL? They're examples of set operators, and they come in handy when you need to combine information from multiple tables or queries. In this article, we'll take a closer look at them. SQL queries let us choose the most important bits from large amounts of information. Of course, we can't expect that all necessary data will be stored in one table.
20 Jun 2017
Useful SQL Patterns: Date Generator
As you start coding in SQL, you will use some statements and techniques over and over again. We call these “SQL patterns”. This series will look at the most common SQL patterns and consider how to use them. SQL patterns, such as the pivot pattern we discussed last week, can save you a lot of time and effort. Suppose you are asked to get a range of days in a financial quarter, but the only records you have are for the start and end dates of each quarter.
18 Jun 2017
Useful SQL Patterns: Pivoting
As you start coding in SQL, you will use some statements and techniques over and over again. We call these “SQL patterns”. This series will look at the most common SQL patterns and consider how to use them. The concept of pivot in SQL refers to taking the data in table rows and making that data into columns. This is very important in reporting, and it’s easy to do when you use the CASE statement.