Databases

This post will explain how user accounts by default work in PostgreSQL, and how you can change the default password. PostgreSQL works a bit differently to other database servers like MySQL when it comes to the default behaviour of user accounts, so read on to find out how to manage access as the default PostgreSQL admin user. PostgreSQL uses the system users The default PostgreSQL configuration uses ident for authentication – this method uses the hosts operating systems usernames and compares them against the permissions stored for each database. This means … Read more

This article will demonstrate how to list the PostgreSQL clusters on your Linux system, and how to switch the active cluster. PostgreSQL is one of the most popular relation database servers. Multiple versions can be installed on the same host, so being able to switch between them is pretty useful. Read on to find out how to do it. What is a Cluster A PostgreSQL cluster is a collection of PostgreSQL databases with a shared configuration, managed. This configuration includes things like the executable that manages the … Read more

This tutorial will show you how to import data from a CSV file into a PostgreSQL database table. What is a CSV File A CSV (Comma Separated Values) file is a text file that contains tabulated information. The rows in this data each take up a line in the text file, while the values in each column on each row are separated by a comma – hence, comma-separated. CSV files are versatile. Because the data within is stored as plain text, they can be opened … Read more

This tutorial will show you how to export, import, and back up your PostgreSQL clusters and databases. You should regularly back up. It’s one of the most important things you can do as a sysadmin, developer, and even a hobbyist. Losing your data is detrimental to business, and your projects. Losing your family photos sucks too. This article demonstrates the various way to import and export PostgreSQL data so that it can be backed up. This process should be done regularly (or automated!), and performed … Read more

Here is an article outlining several methods for running SQL files in MySQL on Linux/Ubuntu. Whether you’re installing a package, following a tutorial, or restoring a backup – it’s useful to be able to execute an SQL script from a file and have it do all of the work for you, rather than having to type it all out. Most GUI database managers have a simple import option prominently displayed in the menu bar – so here’s how to do it from the command line … Read more

This page serves as the index for our PostgreSQL tutorials. It will be updated as new articles in the series are added. This guide is intended for developers who are just getting started with PostgreSQL and are looking for a simple resource to get them up and running. PostreSQL Guide Introduction: What is PostgreSQL? Why Use It ?

This article is part of the LinuxScrew Guide for Developers Learning PostgreSQL. PostgreSQL is a relational database management system. It is similar to other networked SQL database servers like MySQL/MariaDB and Microsoft SQL, but there are some key differences in features and functionality. PostgreSQL vs Other Database Systems You can see a comparison of PostgreSQL and other database systems here. In short, while MySQL is the most popular open source database system, PostgreSQL is more advanced. PostgreSQL is object oriented, can store a larger number of types … Read more

This quick article will demonstrate how to use the MySQL/MariaDB COUNT function to count the number of records returned by a query. MySQL/MariaDB COUNT Function Syntax COUNT(query) Note that: query can be an SQL query or a string representing a column name Null values found by the query will not be counted The COUNT function will return the number of matching records for a query and should be combined with the SELECT statement to output the result. Example Data The below examples use the following … Read more

Being able to delete data from a table in a database is a pretty important thing – This article will show you how it’s done in MySQL/MariaDB. MySQL DELETE Statement Syntax In its basic usage, the DELETE operator is used in conjunction with a WHERE query to delete records matching that query: DELETE FROM table WHERE query; Note that: table is the table you wish to delete records from query is the query that defines the conditions records should match to be deleted Safety First! Please … Read more

This short article will show you how to list all of the users on your MySQL server. MySQL Users and Permissions MySQL databases usually have access granted to only certain users, each with their own permissions limiting what they can and can’t do on that specific database. As there are often multiple databases on a server, there will be several user accounts – some for different databases, some from different hosts – so it’s useful to be able to list them all out quickly. Command … Read more