Author: Aldo Zelen

Aldo is a data architect with a passion for the cloud. From leading a team of data professionals to coding a data warehouse in the cloud, Aldo has experience with the whole lifecycle of data-intensive projects. Aldo spends his free time forecasting geopolitical events in forecasting tournaments.

How SQL supports data-driven organization

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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.

SQL Indexing 101

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.

SQL Wildcard

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.

SQL Filtering 101

Sometimes, SQL queries return lots of data you don’t need. In this article, we’ll look at a simple example of filtering SQL queries to reduce the complexity of your data. The key to learning how to filter data in SQL is understanding the very basics of Boolean algebra. That’s just a fancy term mathematicians use to describe expressions involving logical values (true/false) and their associated operators (and, or, not, etc.

Key Insights for Mastering SQL Queries Using Tinder Data Example

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.

Short Guide to Most Popular Database Administration Certifications

As an ambitious database administrator, you want to get ahead of the crowd and expand your knowledge. The best way to do that is to get certified in the technology you’re working with. This article and infographic will guide you through the most popular database administrator certifications on the market today. If you’re here, you’re passionate about working with databases, like many other IT professionals. Being a database administrator (DBA) will open up an IT field of pure engineering, with little consideration of the business side of your organization.

Must-Know SQL Terms for Beginners and Pros

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.

How to Become a Database Analyst

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.

18 Most Important SQL Functions to Learn ASAP

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.

How to Draw a Christmas Tree in SQL

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.

Busy Business Professionals: Simplify Your SQL Code with Recursive Queries

Hey SQL users! Are you repeating the same query in every report? Are your queries getting too complicated? Organize them with recursive queries! Too many SQL reports can lead to clutter on your desktop and in your head. And is it really necessary to code each of them separately? Ad-hoc queries can share much of the same SQL code with managerial reports and even regulatory reports. Suppose you’ve been writing basic SQL queries for a while.

Introduction to Reporting with SQL — the Ultimate Tutorial for Business Professionals

Working with the financial aspects of large and small enterprises can be a daunting task for a business professional. In this article, we’ll look at several ways of constructing the perfect SQL report. You’ve probably already heard about SQL from your colleagues or in other areas of your career. If you’re here, you’ve likely concluded that learning SQL will make your professional life easier – and you’re right!

Non-Syntactic SQL Errors Spotted

A look at common errors that arise when writing code as an SQL beginner. Debugging, Headaches, and SQL If you’re new to SQL, you’ve probably already run into a myriad of errors. Don’t worry — you’re not alone. All developers make mistakes; it’s a normal part of the development process. The key to mastering any programming language, SQL being no exception, is understanding where the most common mistakes lie.

Organize Your SQL Queries with CTEs

Common table expressions (CTEs) allow you to structure and organize your SQL code. Being able to write organized queries is a necessity when you begin to move deeper into SQL, so if you want to become an SQL master, you need to know CTEs. The CTE has been part of standard SQL for some time now. CTEs – which are also called WITH statements – are available in all major RDBMS.

Long SQL Query vs. Recursive SQL Query

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.

Common SQL Window Functions: Positional Functions

Positional SQL window functions deal with data’s location in the set. In this post, we explain LEAD, LAG, and other positional functions. SQL window functions allow us to aggregate data while still using individual row values. We’ve already dealt with ranking functions and the use of partitions. In this post, we’ll examine positional window functions, which are extremely helpful in reporting and summarizing data. Specifically, we’ll look at LAG, LEAD, FIRST_VALUE and LAST_VALUE.

Common SQL Window Functions: Using Partitions with 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 (or 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.

Common SQL Window Functions: Using Partitions with 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 (or 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.

Common SQL Window Functions: Ranking Functions

Want to learn how to use SQL window functions? Ranking functions are a good place to start! 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. These operations are more complex than those used in OLTP systems.

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.

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. Pivoting 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.

Useful SQL Patterns: Conditional Summarization with CASE

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. Previously, we looked at the SQL pattern of matching NULLs. This is important when you are comparing columns containing NULL values. Today, we’re going to consider another SQL practice: conditional summarization with CASE operator.

Useful SQL Patterns: Matching Nulls by Masking Nulls

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. In database development, SQL developers often find themselves returning to the same SQL statements. Learning about these now, early in your SQL journey, will help you work more efficiently. Today, in the first post of this series, we will consider the match by null SQL pattern.

Oracle Top-N Queries for Absolute Beginners

It’s common to run a query using only part of a dataset – for example, the top 100 salespeople in a company. In this article, we’ll see how to use Oracle’s Top-N query method to query just these rows. Top-N queries retrieve a defined number of rows (top or bottom) from a result set. In other words, they find the best or worst of something – the ten best selling cars in a certain region, the five most popular routers, the 20 worst-performing stores, etc.

Understanding Numerical Data Types in SQL

-- Working with databases of any kind means working with data. This data can take a couple of predefined formats. As you start on your learning path with Vertabelo Academy, you will start to understand SQL’s different data types. In this article, we will cover the numeric data types of ANSI SQL. We’ll also examine some functions that convert data from one type to another.

5 Books That Will Grow Your SQL Skills

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.

OLTP vs. OLAP — What’s the Difference?

There are two major camps in the relational database development world: OLTP and OLAP. In this post, we consider the differences and similarities of these two systems. First of all, both OLTP (on-line transactional processing) and OLAP (on-line analytical processing) are used in business applications, especially — although not exclusively — in data warehousing and analytics. Together, they form the two different sides of the analytics/warehousing coin: storing and manipulating the data on one hand and analyzing it on the other.

A Day in the Life of an SQL Developer

Describing a “typical” day for an SQL developer is not easy. When your daily work is using various technologies to create interesting database-oriented products, very few days are alike! Each day brings a new and intriguing challenge. Nevertheless, I’ll have a go at explaining what everyday things an SQL developer might do. Morning: Arrive at Work The cornerstone of any software engineering endeavor is caffeine, and lots of it.

Text Data Types in SQL

How can you store textual information in database tables? Read this post to discover your options. Note: This post is intended for readers familiar with SQL data definition language (DDL) and the DDL CREATE statement. To learn more about DDL, check out Vertabelo SQL Academy. Most data types are classified as NUMERIC, CHARACTER, or DATE. In this post, we’re going to focus on TEXTUAL or CHARACTER data types. These data types handle groups of alphanumeric characters – i.

Refine Results with SQL Set Operators

Using UNION, UNION ALL, EXCEPT, and INTERSECT to manage SQL query results. The function of SQL set operators is pretty simple; they allow us to combine results from different SQL queries into one result set. The best way to understand how set operators work is to use visual methods like the Venn diagram. For those of you not familiar with Venn diagrams, they are two circles that represent items or collections of items.

6 Ways You Can Learn SQL

Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, we have a lot of options! But we then come to a new roadblock. Where to begin? How will we know which option is best for our budget, skill level, and schedule? This article tackles these questions and gives you a roadmap – or should we say a couple of them – of your journey towards SQL proficiency.

SQL Errors: Five Common SQL Mistakes

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding errors are common in any programming language, and SQL is no exception. In this post, we’ll discuss five common mistakes people make when writing SQL. Watch Your Language (and Syntax) The most common SQL error is a syntax error.

SQL Errors: Five Common SQL Mistakes

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding errors are common in any programming language, and SQL is no exception. In this post, we’ll discuss five common mistakes people make when writing SQL. Watch Your Language (and Syntax) The most common SQL error is a syntax error.