Converting Subqueries to Joins

join subquery, join subquery mysql, left join subquery mysql, sql server join subquery, join subquery oracle, how to join two subqueries in sql, mysql inner join subquery, left join subquery oracle, how to join a table with a subquery

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. However, in some cases a subquery can be replaced with

Continue Reading

How It Works

Brush up on your data science and SQL skills with Vertabelo Academy’s interactive courses. Why Vertabelo Academy? You get instant access to lessons that teach various concepts of SQL, data science, and programming in R (soon also in Python!). Our courses are appropriate for people who have no prior knowledge of computer science or programming. The only requirement is a web browser. No need to install databases, download example tables, or spend time inventing exercises for yourself. Each course comes with

Continue Reading

Correlated Subqueries in 5 Minutes

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

Continue Reading

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.

Continue Reading

Extracting Data From a String in PostgreSQL

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? There are many reasons why you’d want to use

Continue Reading

12 Best Data Science Resources on the Internet

Data science is hot right now. If you want to learn more about it, where should you go? Online, of course! Check out our favorite data science sites. Whether you’re a beginner or a pro, these are sites you should know. Not so long ago, if you wanted information on a topic like data science, you had to look for it – either at your local library or at a university. Information was golden, and like gold it was guarded.

Continue Reading