Articles Cookbook
8 May 2018
Ignacio L. Bisso

Converting Subqueries to Joins

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.
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17 Apr 2018
Aldo Zelen

Essential SQL Terms to Know 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 SQL 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.
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10 Apr 2018
Ignacio L. Bisso

Learn to Write a SQL Correlated Subquery in 5 Minutes

If you’re familiar with the famous Russian nesting doll, then SQL correlated 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 SQL 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.
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6 Apr 2018
Dorota Wdzięczna

New LearnSQL.com Online Practice: SQL Practice Set

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. That’s why we created our SQL practice set: a pack of SQL online practice exercises meant to help you master your skills. We spend a lot of time not only developing new courses but also speaking with our users and learning what they expect from SQL online practice exercises.
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4 Apr 2018
Aldo Zelen

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.
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29 Mar 2018
Ignacio L. Bisso

Extracting Data From a String: SPLIT_PART in PostgreSQL

Learn how to use split_part in PostgreSQL to extract data from strings. 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 how to do it using split_part in PostgreSQL, i.e. a string-related function that can be used to extract a substring.
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27 Feb 2018
Jeffrey Edison

How to Start Thinking in SQL

Thinking 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. If you want to know how to write better SQL queries, you have to change the way you think about the code. One of the greatest skills you can have in SQL programming is the ability to change an existing SQL query so you get the results you need.
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9 Feb 2018
Ignacio L. Bisso

How to Remove Junk Characters in SQL

Unwanted characters in text data can be a bit of a pain, but there’s an easy way to fix them. Scroll down to learn how to remove junk characters in SQL in the easiest way! Sometimes, we’ll find unwanted 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!
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31 Jan 2018
Ignacio L. Bisso

How to Solve Capitalization Data Quality Issues

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.
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5 Jan 2018
Aldo Zelen

18 Useful Important SQL Functions to Learn ASAP

Learning a new programming 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 useful SQL functions that you need to know. Structured Query Language, commonly known as SQL, is the standard language for managing and querying data in relational databases. Born out of the need to efficiently interact with large datasets, SQL has become an indispensable tool for database administrators, data analysts, and developers alike.
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