Converting Subqueries to Joins

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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

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SQL Hacks To Control Family Budget On Black Friday Weekend

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

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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. Often, SQL errors are grouped into two categories: syntactic and non-syntactic.

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An Illustrated Guide to Multiple Join

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

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An Illustrated Guide to the SQL Non-Equi Join

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. These are called non-equi joins, and they’re what we will

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An Illustrated Guide to the SQL Self-Join

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. A self-join

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