18+ Best Online Resources for Learning SQL and Database Concepts (2018 revision)

learning sql

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. We’ll start with websites that focus on SQL syntax and basic SQL concepts. 1. Vertabelo Academy Vertabelo Academy offers

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SQL joins

A SQL JOIN is a method to retrieve data from two or more database tables. This article presents a basic overview of what data from a particular SQL join will look like. A popular way of understanding SQL joins is to visualize them using Venn diagrams, so each example have corresponding Venn diagram, appropriate SELECT statement and the result table. There are a few major kinds of SQL joins: INNER JOIN OUTER [LEFT | RIGHT | FULL] JOIN NATURAL JOIN

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How to Tackle SQL NULLs: The NULLIF Function

Usually we try to avoid NULLs, but sometimes we need to have a NULL instead of an actual value. When this need pops up, a helpful but little-known SQL function called NULLIF makes it possible. This post will introduce you to NULLIF and demonstrate its use in two example cases. In the article How to Tackle NULLS: The COALESCE Function , we got to know the COALESCE function. It returns the first not-null expression. The NULLIF function works differently. It

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How to Tackle SQL NULLs: COALESCE function

It’s inevitable that some data in the database has no value what in SQL is represented by the NULL keyword. “No value” here is different from zero, false, or an empty string (but with exceptions! In Oracle database, NULL is the same as string of zero length). During playing with the database, treating NULLs are becoming more and more troublesome, therefore SQL standard provides help with some of the functions, like COALESCE. Let’s introduce the COALESCE() function: Definition COALESCE function

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