16 March 2023
16 March 2023

The SELECT Statement in Oracle

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The SELECT statement is used to retrieve information from a database. Following the execution of a SELECT statement, a tabular result is held in a result table (called a result set). It allows you to select the table columns depending on a set of criteria. SELECT statements might be as straightforward as selecting a few … Read more
02 March 2023
02 March 2023

Retrieving MySQL data from within Python

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Applications of all types commonly access MySQL to retrieve, add, update, or delete data. The applications might be written in Python, Java, C#, or another programming language. Most languages support multiple methods for working with a MySQL database and manipulating its data. The approach you take when accessing MySQL will depend on the programming language … Read more
21 February 2023
21 February 2023

PostgreSQL Basics: Object Ownership and Default Privileges

In the first security article, PostgreSQL Basics: Roles and Privileges, I discussed how roles (users and groups) are created and managed in PostgreSQL Depending on your background with permissions, particularly in other database products, some of those nuances in how permissions work may have been surprising. Understanding how roles and privileges work in Postgres is … Read more
06 February 2023
06 February 2023

Using TOP clause in a SELECT statement

There might be a time when you might want to return just a few rows of a result set, instead of the complete set. This might be useful if you want to just validate a selection criteria or a few rows of data. For whatever the reason the TOP clause can be used to return a specific number or a percentage of rows from a result set. This article will cover using the TOP clause in a SELECT statement and how it can be used to return a partial set of records.… Read more
02 February 2023
02 February 2023

PostgreSQL Constraints: Learning PostgreSQL with Grant

One of the most important aspects of data management is the ability to ensure that the data in your database is well defined and consistent. Some aspects of that are ensured through the relational data structures you design. Another piece of control is using the correct data type. Then, we get to constraints. A constraint is a way to validate data prior to adding it to your database. This is one more tool in the toolbox that helps you maintain good data.… Read more
31 January 2023
31 January 2023

Optimizing Queries in MySQL: Optimizing Reads

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Optimizing read operations is one of the most prominent problems concerning any database administrator. No matter what kind of database management system is in use – MySQL, its flavors like Percona Server or MariaDB, MongoDB, TimescaleDB, SQL Server, or others, read queries are a concern. The primary read query example is SELECT queries, but a lot of this pertains to UPDATE and DELETE as well since they too have to fetch rows to be operated on.… Read more
19 January 2023
19 January 2023

PostgreSQL Basics: Roles and Privileges

Information security, whether in databases, applications, or larger IT systems, is based on the principles of Authentication and Authorization, often referred to as AuthN and AuthZ respectively. Likewise, PostgreSQL security involves creating roles that allow access to server resources (AuthN) and then granting privileges to database objects appropriately (AuthZ). Understanding how each of these components work together is essential to effectively manage security in a PostgreSQL cluster.… Read more
17 January 2023
17 January 2023

Manage Data Over Time with SQL Server MERGE Statement

Once data is in a table it needs to be maintained. New records will need to be added, and existing records will need to be updated, and/or deleted. To keep data maintained, the insert, update or delete actions may need to be performed. This article will show how those three data manipulation language (DML) actions can be synchronized together within a single basic MERGE statement.… Read more
09 January 2023
09 January 2023

Index Types in PostgreSQL: Learning PostgreSQL with Grant

As with any other relational data management system (RDBMS), PostgreSQL uses indexes as a mechanism to improve data access. PostgreSQL has a number of different index types, supporting different behaviors and different types of data. In addition, again, similar to other RDBMS, there are properties and behaviors associated with these indexes. In this article I’m going to go over the different types of indexes and some index behaviors. We’ll get into what the indexes are, how they work, and how best you can apply them within your databases. I’m hoping you’ll develop an understanding of which indexes are likely to work better in each situation.… Read more
05 January 2023
05 January 2023

Introducing the MySQL common table expression

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As with many relational database management systems, MySQL provides a variety of methods for combining data in a data manipulation language (DML) statement. You can join multiple tables in a single query or add subqueries that pull data in from other tables. You can also access views and temporary tables from within a statement, often … Read more
02 December 2022
02 December 2022

Subqueries in MySQL

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A subquery is a type of query that is embedded—or nested—into a data manipulation language (DML) statement. The data returned by the subquery is passed into the DML statement and incorporated into its overall logic. The subquery itself is typically a SELECT statement, although you can also use a TABLE statement or VALUES statement. Even so, the SELECT statement continues to be the most common choice for subqueries, and that’s the one I focus on in this article.… Read more
12 November 2022
12 November 2022

Introducing the MySQL DELETE statement

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In the last few articles in this series, you learned about three important data manipulation language (DML) statements: SELECT, INSERT, and UPDATE. The statements make it possible to retrieve, add, and modify data in a MySQL database. Another DML statement that is just as important is DELETE, which lets you remove one or more rows from a table, including temporary tables. In this article, I focus exclusively on the DELETE statement to help round out our discussion on the core DML statements in MySQL. Overall, the DELETE statement is fairly basic, but one that’s no less necessary to have in your arsenal of DML tools. … Read more