8 Tips Absolute Beginners Can Use to Fix SQL Queries

Fix SQL Queries
Code errors are common – and frustrating. And when you’re just learning SQL, it can be very challenging to find and fix your mistakes. In this post, we’ll show you eight ways to solve or eliminate common SQL coding errors. Today, we’ll talk about some tips the SQL beginner can use to avoid several common errors. These tips work in any database environment. As we go along, we’ll be showing some error messages.

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.

Correlated SQL Subqueries For Newbies

Correlated subqueries are the only way to solve some SQL statements. But they can be very slow. In this post, we’ll talk about why, how, and when to use them. Subqueries are an important resource for increasing the expressive power of SQL. If you haven’t read our previous article, subqueries are simply a SELECT statement inside another SELECT. We can use them in different places inside a SELECT, such as in the WHERE, HAVING, or FROM clauses.

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.

GROUP BY Clause: How Well Do You Know It?

The database can do different kinds of computations: it can add and subtract, multiply and divide, it can do computations on dates, it can count rows and sum row values, and so on. It can also do quite sophisticated statistics. The GROUP BY clause is the most basic way to compute statistics in SQL. It can be quite tough for beginners but it is really powerful. Let’s look at the details of the GROUP BY clause, starting with the basics.

Do It in SQL: Recursive Tree Traversal

In the previous article, I described how to use Common Table Expressions to find the shortest path in a directed graph. That example could be hard to follow, I admit. Let’s do something much more common, something that is implemented on almost every website – a menu. But… we’ll do as much as possible in a single SQL query instead of writing the code. We’ll use CTEs for PostgreSQL and the hierarchical query clause for Oracle.

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:

SQL Subqueries

The article describes what a subquery is and what these useful statements look like. We will cover basic examples with the IN, EXISTS, ANY, and ALL operators, look at subqueries in from and where clauses, and explore the difference between correlated and nested subqueries. First, let’s start with an example database. To present some of these statements we need to have an example table and fill it with some data.

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.

SQL JOIN Made Easy

You’re probably already familiar with simple SQL queries, such as “SELECT * FROM table”. Now you are wondering what to do when you have multiple tables and you want to join them. Exactly! JOIN is the key. In this tutorial, you will learn how to connect data from multiple tables using SQL JOINs. What are SQL JOINs? Databases usually have more than one table. JOINs are an SQL construction used to join data from two or more tables.

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 >MySQL standard provides help with some of the functions, like COALESCE.

Why Should I Learn SQL?

There are 250+ computer programming languages in popular use. Why should you learn SQL, or Structured Query Language? Why Should I Learn SQL? Are you interested in boosting your career? Wondering what skills are worth investing in? If you’re currently in your dream job, still searching for it, or even thinking about starting your own business, it pays to develop your technical skills. A solid technical background is highly in demand among recruiters, and it provides the necessary underpinnings for managing the IT side of your business.