In this article, I will cover perhaps the most important element of the SQL language. That's right! I'm talking about the SQL INNER JOIN clause. As you know, in a database the data are stored in several tables. In my last article, I covered how to create SQL queries when the data you need is in only one table. But what if the data you need is in two tables?
Find out why you should forget about Excel and start using SQL even if you’re not an IT expert. We’ll show you how easy it is to learn SQL, how it can make you work better, and how Vertabelo Academy makes the learning process fun. “I Don’t Deal With Data” We frequently hear the sentence above from people outside the IT industry. Well, it’s not entirely true. Data is now almost everywhere.
In my last article, I roughly described how standard SQL differs from T-SQL and who should learn which. Now I’d like to focus on the syntax differences and illustrate these differences with examples. If you think T-SQL is an extension implementing all the features from standard SQL, you aren’t right. However, in SQL Server you will find almost all the features of the SQL standard. In this article you will find examples of some of the differences in syntax between standard SQL and Transact-SQL.
So you want to learn SQL and decided to learn with Vertabelo Academy? That's great! This article show you the sequence in which to take the courses in order of increasing difficulty. Courses Teaching Standard SQL (ANSI) If you plan to begin learning SQL and would like to become a professional, your first step is to complete the SQL Basics course. This is the fundamental course that will provide a smooth introduction to the world of relational databases by learning about tables.
If you are beginning to learn SQL and are confused by the differences between SQL and other similar languages like T-SQL, this article will help make things clear. You will also find explanations concerning which topics would be better to start learning first: general SQL or something more specific like MS SQL Server. What is SQL? SQL (Structured Query Language) is a basic ANSI/ISO standard programming language designed to operate on data stored in relational databases.
Do you think learning SQL will help you in your career? You are right. SQL is one of the easiest computer languages to learn. These days many non-IT employees have SQL skills and use them to extend their professional capacity. Moreover, more and more companies are encouraging their employees in non-IT areas (like sales, advertising, and finances) to learn and use SQL. One of the benefits of empowering employees with SQL skills is that once you answer one data question, the results will generate a new data question, and then perhaps a cascade of further data questions.
-- -- We did it again! Each year, we review all SQL courses and tutorials on the market to help you find the best online resources to learn SQL. Find out which SQL courses are worth a try! But let's get to the point and take a closer look at some of the best online resources that can help beginners get started with SQL.
Thinking about using Microsoft SQL Server? If so, you’re in the right place. In this article, we’ll look at the Microsoft SQL Server platform and go over its pros and cons. We’ll also evaluate the platform from both a company’s and a data specialist’s perspective. What Is Microsoft SQL Server? In technical terms, Microsoft SQL Server is a relational database management system (RDBMS) developed by Microsoft. Essentially, it’s software that allows you to store, change, and manage relational data effectively.
Knowing how to improve SQL query performance is an important skill, especially when working with with large databases. In this article, you’ll learn how to write more efficient SQL queries to get results faster. The biggest difference between SQL and other languages is that SQL is a non-procedural language. In a non-procedural language you specify the results that you need but not the methods used to get it. The advantage of a non-procedural language is that it is easier to write programs, therefore it is common for non-programmer business users to generate reports from SQL queries.
Typical business users make decisions based on gut feelings, but this can’t get them so far. In this article, we’ll look at how learning to write basic SQL queries helps your company become a data-driven organization. Businesses face many decisions. Do we increase our advertising budget in one region or the other? Are certain products selling quickly enough? What we should do if they aren’t? Most of these decisions are driven by intuition, but organizations that make the most business impact use data-driven decision-making.
Microsoft SQL Server is one of the most popular professional database servers on the market. In this guide, we’ll help you install SQL Server on the Windows operating system together with SQL Management Studio. How to Install SQL Server 2017 We’ll install SQL Server 2017 in this guide. You can download it for Windows and Linux, but you can’t install Microsoft SQL Management Studio on Linux at the moment, so we recommend you stick to Windows.
In this article, I’ll help you write and execute your first SQL query. Let’s jump right in! Running an SQL query for the first time is not a complex task, but it can seem intimidating at first if you’re a complete beginner. But once you get past that initial roadblock, you’ll be able to focus on learning SQL and writing more interesting queries to meet your business needs. The Ingredients You’ll need these three things to run an SQL query:
How much SQL do you know? Test your knowledge with this crossword to find out! Contest Rules Download Vertabelo Academy SQL crossword. Solve tasks and unlock its solution. Send your answer at email@example.com before👉 September 8, 2018. Wait and win a special prize 💜 Prizes will be drawn among the users who will send us the correct solution. Then winners will be contacted by email within 7 days from contest closing.
Indexes are one of the most misused and misunderstood entities in physical database design. A good understanding of indexes and how they solve database performance problems is necessary for any database novice. In this article, we’ll look at basic database indexes and their role in database development. To picture what an index is, consider a textbook. At the end of most textbooks is an index listing all the terms one can find in the text and the pages on which they appear.
Three years or three months? With all the 12-week bootcamps and coding schools out there, three years sound like a joke. “Enroll in our course today, and become an expert programmer!” “Start learning to code and jumpstart your programming career immediately!” Most probably, you’ve heard lots of claims like these if you’re interested in coding. Are they reassuring? Maybe. Frustrating? Sometimes. If you’ve been learning for a year and still feel like a newbie programmer while others are starting their careers in three months, you start to wonder: What’s wrong with me?
SQL wildcard allows us to filter data matching certain patterns in SQL. We use wildcards with the LIKE operator in the WHERE clause of an SQL query to filter data. In this beginner’s article, we’ll look at everything you need to know about basic SQL wildcards. If you like playing cards, then you know that wildcards can substitute any other card in your deck. Similarly, wildcards in SQL strings can substitute one or more characters.
If you plan to learn SQL online but aren’t sure where to start, you’re in the right place. I evaluated the top 7 ranked SQL online courses to help you find the right solution. While summer’s a great time to relax and get away from work, it’s also an excellent opportunity to learn new skills—like SQL! Thanks to online schools, learning new tech skills is super easy, and you can choose from a variety of formats to suit your needs, like courses and tutorials.
Think summer is reserved for flying to warm places and hanging out at the beach? Sure! But it’s also a great time to learn new skills that you haven’t had time for. If you recently graduated from high school and want to get a head start on computer programming for college, learning SQL over the summer is a great opportunity. You have nothing to lose and everything to gain—SQL is actually really easy to learn, especially with so much free time over the summer.
Why is June 21 the official start of summer? Let’s see how SQL can help us answer this question. The Summer Solstice Officially, June 21 is recognized as the summer solstice, the longest day of the entire year in terms of daylight. Why? Because on this day, the sun rises early and sets quite late. People in the Northern Hemisphere celebrate the summer solstice with feasts, bonfires, picnics, and traditional dances and songs.
Going from zero to one can be daunting in any endeavor. The same is true for learning new programming languages, even simple ones like SQL. In this article, we’ll take a look at some key insights that will help you understand the nuances of SQL queries. If you’ve never used SQL, you’re in the right place. When learning anything new, you’ll find that there are always some key insights or tips that can help you on your way.
As SQL users, we usually focus on writing queries that return correct results. However, there are more things to consider when you’re writing a query; one of them is query performance. In this article, we’ll look at some examples where query response time is critical. Scene One: 911 Call Center Let’s suppose we’re at a 911 call center, when the phone rings. One of the operators answers the call; a witness reports that a man has been shot.
Will robots replace humans in the near future? As machine learning and artificial intelligence continue to grow in popularity, this question becomes all the more relevant. Which jobs will become extinct, and what will society looks like in the future? If you’re a data analyst whose worried about their job security, don’t worry—there’s still hope for you! In this article, we’ll take a look at the skills a data analyst can acquire to become a data scientist and rise above these pesky robots 🙂
There are many perceptions of IT, one of the fastest growing industries in the world. For a non-technical person, IT is usually associated with high salaries, numerous job offers, and elite clubs. But IT is more than just people earning big bucks for writing code. The most valuable part of the IT industry is its community. The first steps are the hardest As a complete IT newbie, I had lots of doubts and fears about entering the IT industry.
Not all queries are alike, especially in terms of performance. In this article, we’ll look at how you can convert SQL subqueries to joins for improved efficiency. When should I use SQL subqueries? Great question! Unfortunately, there’s no concrete answer. SQL beginners tend to overuse subqueries. Typically, once they find that SQL construction works in one situation, they try to apply that same approach to other situations. It’s only natural.
Working with databases can seem daunting to a non-technical person. Right away, you’re bombarded with new terms that make your head spin. Database, database instance, table, SQL and others are some of the basic terms that you need to understand just to have a normal conversation with your technical colleagues. In this article, we’ll explore some basic database terminology you need to know to succeed. Imagine you’re attending a meeting with the development staff and suddenly feel as if you’re listening to white noise.
If you’re familiar with the famous Russian nesting doll, then SQL subqueries should be a peace of cake to understand—subqueries are just queries nested within queries. An SQL subquery is often called an “inner” query; the main query is usually called the “outer” query. This article covers everything you need to know about correlated subqueries. What Exactly is a Correlated Subquery? A correlated SQL subquery is just a subquery that is executed many times—once for each record (row) returned by the outer (main) query.
If you’re looking to retrieve any kind of information from a database, you need to speak its language. But querying databases is an art—and it demands practice. We spend a lot of time not only developing new courses but also speaking with our users and learning what they have to say about online learning. This is how we came up with the idea of creating an SQL practice set.
Curious about becoming a database analyst? Maybe you’ve taken some database courses at university and they really struck a chord. Or maybe you learned online. Now you’re thinking about making a career out of working with databases. Where would you start? What should you expect at each phase of your professional development? In this post, we’ll explore the challenging and exciting world of databases analysis. We’ll go from the very beginning of a career to the apex of professional success.
Learn how to extract data from strings in PostgreSQL using the split_part function. Quite often, we’d like to extract parts of a string when working with text values. A common example is when we have a full name and need to retrieve only the last name. In this article, we’ll examine split_part, a PostgreSQL string-related function that can be used to extract a substring. Why Use String Functions in Your Database?
We asked our users why they decided to learn SQL. This is what we’ve learned. At Vertabelo Academy, we help people with no computer science backgroundto understand the core concepts of databasesand data science. For example, we teach users how to extract the most important data from a database to build simple reportsand how to understand key statistical metrics in data analysis. We love to provide easy-to-understand examples that thoroughly depict complex technical concepts.
Learning to think in SQL will help you understand what SQL queries do, how to create and change them, and how to create reports from the data you obtain. One of the greatest skills you can have in SQL programming is this the ability to change an existing SQL query so you get the results you need. When you are first starting out, you likely will not create SQL queries from scratch but rather reuse what others have written.
We recently published a story from a Vertabelo Academy user who found her love thanks to SQL. On a similar note, I asked my colleagues to bring back old memories of writing their very first scripts. And yes, love is involved. Here at Vertabelo Academy, we’ve got some real OG programmers and data scientists making great content. They fell in love with data way before it was cool—and easy. So today, we’re jumping back in time to see what it was like to learn SQL before the Internet and Vertabelo Academy courses existed.
They say that if you do what you love, you’ll never work a day in your life. At Vertabelo Academy, we strongly believe in this adage. We’re creating courses because it’s what we enjoy doing. We’re passionate about SQL and data science, and we want to deliver the best content possible in these domains. To that end, we provide our users with practical modules because learning by doing is the best way to master a new skill.
Just in time for Valentine’s Day, we discover which of Gary and Sara’s friends are in love – and how to use the SQL JOIN statement to work with data in multiple tables! Did you know SQL is a matchmaker? That’s right; it loves to make data couples by linking information from two (or more!) tables using the JOIN statement. However, many SQL rookies run into problems using JOIN. So let’s go to a party and learn how to use JOIN the right way!
Unwanted characters in text data can be a bit of a pain, but there’s an easy way to fix them! Sometimes, we’ll find extra characters inside our string data because our SQL queries didn’t work as expected. Moreover, these extra characters may sometimes be invisible, which really complicates things. In this article, we’ll examine some string-related SQL functions that can handle unwanted characters—visible or not! The Importance of Standardizing Strings in Your Database When we work with data populated or loaded as free text, the data quality is often quite poor.
Misspelled names, typos, and text data quality issues in your database? Power up your queries! Use SQL string functions to address data quality issues related to capitalization. Sometimes, our SQL queries don’t work as expected because of data quality issues. In this article, we will examine some string-related SQL functions that can correct data quality issues related to capitalization. We’ll be using PostgreSQL in our examples, but similar functions are available in most database engines.
For this post, I’ve gathered 15 of the most interesting SQL articles published in 2017. If you’re an SQL beginner and are interested in learning more about databases and SQL queries, or if you’d just like to expand your knowledge of SQL, this article is perfect for you. Let’s dive right in! Top 3 Vertabelo Academy articles I’ll start off the list with three of the most popular Vertabelo Academy articles.
Mastering the basics for a smooth start to SQL Learning a new programing language can seem intimidating. Like any other language, a programming language has a large vocabulary that you need to master. In this article, we’ll look at some of the most important SQL functions that you need to know. SQL is a rich language with many useful functions for working with different data types. Once you practice with some of the most important SQL functions, you’ll gain enough confidence to move on to more advanced material.
Wanna be part of this year’s Christmas success? Santa needs your help organizing his Christmas deliveries. For this occasion, we’ve prepared a special Christmas database. While working on tasks, you’ll help Santa Claus deliver gifts to children. For this upcoming Christmas, we’ve prepared a 24-Day SQL Advent challenge. From now until Christmas Eve, we’ll publish daily SQL tasks for you to complete. If you’ve completed or recently started our SQL Basics course, or if you already have basic SQL knowledge, then this event is perfect for you!
You can use SQL to manipulate all kinds of data, from huge analytical queries to brief single-purpose statements. But you can also use SQL just for fun, without any business requirements stifling your creativity. So, get out your jolly hat and prepare to sing O Christmas Tree as we create some quirky art with plain old SQL. Today, we’re going to generate some holiday-themed ASCII art, just for fun. That’s right.
Though the COALESCE function may seem complex, it’s actually very straightforward and useful. In this short article, we’ll look at several examples of how the COALESCE function can be used to work with NULL values in SQL. The Need for Coalesce Before we dive into the COALESCE function in detail, you should understand how NULL values behave in expressions. Simply put, a value of NULL indicates that there is currently no value for a particular entry in a table column.
Excel is a powerful beast that lets you analyze complex data. Yet, operating on big chunks of data can sometimes be a daunting task. Let’s take a look at how SQL can help. Today, we’ll tackle a common problem with importing data to an SQL database, using a real-life example. Suppose your company conducted a survey on the most popular programming trends and preferences, striving to meet the expectations of its users.
Computing Tardiness: Date, Time, and Interval Arithmetic in SQL In this article, we’re going to discuss some interesting operations we can perform with date-related data types in SQL. The SQL standard, which most relational databases comply with these days, specifies the date-related data types that must be present in relational databases. The most important of such data types are date, time, timestamp, and interval. Here’s a brief rundown of the differences between these data types:
If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.
Thanksgiving is a holiday many Americans celebrate with their families and friends, seated around a table loaded with a hearty feast. The most prominent of all dishes is, of course, the turkey. However, at least a few other specialties are also cooked for Thanksgiving. Do you find it hard to choose what to prepare? If so, we’ve got a solution for you: a special SQL query that will help you pick the best dishes.
In our previous post, we explained how SQL window functions work by example. We started with some very simple, basic functions. Let’s extend it by explaining subclauses in window functions. SQL window functions are a great way to compute results from a set of rows rather than a single row. As you know from our first article, the “window” in window function refers to the set of rows.
Recursion is one of the central ideas in computer science. We can define it as a method for solving problems where the solution of the problem depends on solving a smaller instance of a problem. If this sounds complicated do not fret, in this article we will learn about recursion in SQL that you can practice and deepen in Vertabelo Academy. Recursion is a way of solving hierarchical problems we find in data with common SQL.
So far, our articles in the “An Illustrated Guide” series have explained several join types: INNER JOINs, OUTER JOINs (LEFT JOIN, RIGHT JOIN, FULL JOIN), CROSS JOIN, self-join and non-equi join. In this final article of the series, we show you how to create SQL queries that match data from multiple tables using one or more join types. Join Types in SQL Queries Before we start discussing example SQL queries that use multiple join types, let’s do a short recap of the join types we’ve covered so far, just to be sure you understand the differences.
Did you know that an SQL join doesn’t have to be based on identical matches? In this post, we look at the non-equi join, which uses ‘non-equal’ operators to match records. We’ve already discussed several types of joins, including self-joins and CROSS JOIN, INNER JOIN and OUTER JOIN. These types of joins typically appear with the equals sign (=). However, some joins use conditions other than the equals (=) sign.
What is an SQL self-join and how does it work? When should it be used? We’ll provide answers to those questions! In SQL, we can combine data from multiple tables by using a JOIN operator. JOIN has several variants; we’ve already discussed CROSS JOIN, INNER JOIN, and OUTER JOIN. Most of the time, these operators join data from two or more different tables. In this article, however, we will explain how to join records from the same table.
Everyone, from rookie programmers to SQL ninjas, needs a bit of help now and again. Enter Vertabelo's SQL Cheat Sheet! Working with databases is hard. There's a lot of data to manage, which can be daunting. But the main challenge many database users face is the SQL commands themselves. It's all right when you're using the same familiar ones day after day, but what about the commands you dust off once or twice a year?
When it comes to information management, duplicates present one of the most common challenges to data quality. In this article, I’ll explain how it is possible to find and distinguish duplicate names with the help of the SQL data programming language. I really like my maiden name. The reason I like it so much is because it’s rare. My maiden name (first with last) provided a unique identifier on platforms such as LinkedIn, Facebook, Twitter and similar.
Isn’t data science way too advanced for simple SQL? Nope! SQL can help you build a foundation for your data science career. Let’s see how. Data science is hot right now. What if you could predict the next market crash? Or contain the spread of Ebola? Or accurately predict a health crisis months or even years before it happens? Data scientists are working hard on these kinds of projects, and they are earning healthy salaries in the process.
Anyone can learn SQL. It’s not as hard as you think! In today’s world, even those in non-technical jobs need some technical skills. And you don’t have to be a hard-core nerd to get these skills. Let me tell you my own story. A few years ago, I wasn’t considering learning SQL or anything else that I labelled “technical”. My background is in sociology, journalism, and scriptwriting, and I thought computer languages were pretty sci-fi.
Foreign keys and referential constraints allow you to set relationships between tables and modify some of the database engine’s actions. This beginner’s guide explains referential integrity and foreign key use in MySQL. One of the most important aspects of database usage is being able to trust the information you store. Database engines provide several features that help you maintain the quality of your data, like defining required columns as NOT NULL and setting an exact data type for each column.
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.
Jane has a data problem and an overdue report. Will SQL save the day? Jane works as a business analyst for a large London bank. As she walks to the station on Monday morning, she’s thinking about last week’s unfinished work. She couldn’t get the data she needed from IT, so she could not deliver her report on a financial product’s non-performing assets. She absolutely must submit the report to her manager today; she’s already delayed it for more than a week.
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? INNER JOIN combines data from multiple tables by joining them based on a matching record.
-- -- Previously, we’ve discussed the use of SQL aggregate functions with the GROUP BY statement. Regular readers of the Vertabelo Academy 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.
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:
-- -- When you need to combine information from multiple tables or queries, SQL set operators are a useful tool. 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. Let’s say we want to present every aspect of some key data group in one results table (e.
The JOIN statement lets you work with data stored in multiple tables. This article is a practical introduction to the SQL JOIN. Imagine if you could only work with one database table at a time. Fortunately, this isn’t anything we have to worry about. Once you learn the JOIN statement, you can start linking data together. This article will give you examples that illustrate how we use JOINs, how each type of JOIN works, and when to use each type.
“Learn SQL the Hard Way” by Zed A. Shaw is a great ebook for those who want to learn SQL essentials. At $19.99 USD, it may seem a bit expensive for an ebook, but you’re getting a DRM-free PDF, plus a whole bunch of explanatory videos and additional files. Who should read “Learn SQL the Hard Way”? Anyone interested in SQL basics – modifying databases or selecting information. Make no mistake about it: this book focuses heavily on the practical side of database language.
Which books will help you build your database skills? We look at five awesome SQL books. There’s a common saying that “all wise men read books”. I would say that all professionals read books – particularly those related to their field. There are many books about databases and SQL; most are tied to specific vendors (DB2, Oracle, MS SQL) but there are also plenty that are vendor-neutral. In this article, I’m going to review a few books that I would recommend to SQL learners at various levels of proficiency.
Vertabelo Academy is a great place to learn SQL. If you’re a complete beginner, it’s best to have an overview of what SQL is, what a database is, and how they work together. In this article, you’ll find a quick explanation of all you need to get started with SQL. The Database You might have already heard that SQL is used with databases. What exactly is a database? In the most general sense, it is an organized collection of various kinds of data.