Tag: what is

What is an ER Diagram?

Posted on by Ian

An entity relationship (ER) diagram (also known as an ERD for Entity-Relationship Diagram) is a visual representation of the relationships between entities within a system. ER Diagrams are often used when designing relational databases. An ERD serves as a blueprint for designing a database by depicting entities, their attributes, and the relationships between them.

ER diagrams help in conceptualizing the structure of a database and serve as a communication tool between database designers, developers, and stakeholders.

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Understanding the CONTINUE Keyword in SQL Server WHILE Loops

Posted on by Ian

WHILE loops are a fundamental construct in T-SQL (and in programming in general) for executing repetitive tasks. Within these loops, the CONTINUE keyword serves as a powerful control flow tool, allowing developers to skip iterations and optimise loop execution.

This article explores the usage and benefits of the CONTINUE keyword in SQL Server WHILE loops.

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Indexed Views in SQL Server: A Complete Guide

Posted on by Ian

Indexed views can significantly enhance the performance of complex queries in SQL Server. However, they come with several prerequisites and considerations that need to be carefully understood before implementation.

In this article, I provide an overview of indexed views, discussing their utility, prerequisites, and best practices, along with performance considerations and a simple example.

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What Does Deterministic Mean in SQL?

Posted on by Ian

In SQL, a deterministic expression or function always returns the same result when given the same input. Conversely, a nondeterministic expression or function may return different results even with the same input due to factors like system time, randomization, or external data changes.

Below is a quick overview of the differences between deterministic and nondeterministic functions/expressions.

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How SQL Constraints Work: A Beginner’s Overview

Posted on by Ian

Constraints are an important concept in relational database management systems (RDBMSs). Whenever we design a database, we need to ensure that it will be able to enforce data integrity, by checking or restricting what the user can enter to only data that conforms to the rules of the database. That’s where a constraint can help.

This article explores what SQL constraints are, the various types available, their importance, and how they are implemented.

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A Quick Look at the DROP_EXISTING Option in SQL Server

Posted on by Ian

In SQL Server, we can use the DROP_EXISTING option of the CREATE INDEX statement to modify an existing index. It allows us to drop and rebuild an index in one atomic operation. This can be particularly useful when we need to make changes to an index, such as altering its columns, changing its properties, or rebuilding it with different options like fill factor or sort order.

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What is User-Defined Integrity?

Posted on by Ian

Maintaining data integrity is critical for ensuring the accuracy, consistency, and reliability of data inside a relational database. Among the various strategies to enforce data integrity, user-defined integrity plays a significant role, especially in customized applications and systems where standard integrity constraints may not suffice.

This article explores the concept of user-defined integrity, its importance, how it is implemented, and scenarios where it can become essential.

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What is a One-To-One Relationship?

Posted on by Ian

In relational databases, a one-to-one relationship is a relationship between two tables where each record in the first table corresponds to one and only one record in the second table, and vice versa.

This kind of relationship is less common compared to other relationship types, but it can be useful in certain scenarios. The one-to-many and many-to-many relationships are much more common than the one-to-one relationship in SQL.

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