Introduction

Azure SQL Database is a fully managed relational database service. It offers a high-performance, scalable, and secure database solution without the need to manage infrastructure, such as hardware or operating systems. Key features include:

Key Features

• Managed Service: Automated backups, patching, and updates to minimize maintenance overhead.
• Scalability: Elastic scale on demand with options for various compute tiers.
• High Availability: Built-in high availability and disaster recovery with multi-region support.
• Security: Advanced threat protection, encryption, and compliance with industry standards.
• Integration: Seamless integration with other Azure services like Azure Data Factory, Azure Functions, and Power BI.

DTU vs VCU

DTU (Database Transaction Unit)

DTU is a blended metric that represents a combination of CPU, memory, and I/O resources in a single unit. It provides a simplified way to measure and choose the performance level of an Azure SQL Database.

VCU (Virtual Core Unit)

VCPU refers to the number of virtual cores allocated to the database. It provides a more granular control over the compute resources assigned to the database.

Choosing Between DTU and VCPU

If you prefer simplicity and ease of use, DTU may be a suitable choice. If you have specific performance requirements and want more control over the allocation of virtual cores, VCU might be more appropriate.

SQL Elastic Pool

An Elastic Pool is a database service tier that allows you to manage and allocate resources more efficiently for a group of databases. Instead of provisioning resources for individual databases, you can group databases into an Elastic Pool, and they share a common pool of resources.

How Many Databases Can You Add in One Elastic Pool?

• Basic Tier: Up to 5 databases.
• Standard Tier: Up to 500 databases.
• Premium Tier: Up to 5000 databases.

PolyBase

PolyBase is a feature in SQL Server that allows you to access and query data stored in external sources, such as Hadoop or Azure Blob Storage, as if it were part of a SQL Server database. It provides seamless integration of structured and unstructured data, making it easier to analyze and process large datasets from various sources.

What is an External Table, and How is it Used in PolyBase?

An external table in PolyBase is a virtual table in SQL Server that represents the structure of the data in the external source and allows users to query it as if it were a local table.

How to Create an External Table?

• Create a Master Key: If not already created, a master key is used to encrypt the credentials for accessing external data sources.
• Create Data Source Credential: You need to create a credential containing the necessary authentication details (username and password) for the external data source.
• Create External Data Source: Define the external data source, specifying the connection details, such as the server address, port, and data source credential.
• Create External Table: Define the external table, which references the structure of the data in the external source. It serves as a schema definition that allows SQL Server to query the external data source.

SQL Server Management Studio (SSMS)

Azure SQL Server Management Studio (SSMS) is a database management and development tool provided by Microsoft. It is a standalone application that allows database administrators and developers to work with various Microsoft SQL Server products, including Azure SQL Database, SQL Server on-premises, and SQL Data Warehouse, among others. SSMS offers a range of features to help users manage and interact with SQL Server databases.

Dedicated SQL Pool

Azure Dedicated SQL Pool, formerly known as Azure SQL Data Warehouse, is a cloud-based data warehousing service provided by Microsoft Azure. It is designed for storing and analyzing large volumes of data, helping organizations gain insights from their data for business intelligence and analytics.

Dedicated SQL Pool vs Azure Synapse

Dedicated SQL Pool is a specific component within Azure Synapse Analytics. Azure Synapse is a comprehensive analytics service that integrates big data and data warehousing. Dedicated SQL Pool, formerly known as SQL Data Warehouse, is just one part of Azure Synapse, focusing on data warehousing and analytical workloads.

The main difference is that Azure Synapse is the overarching service that includes the Dedicated SQL Pool, which is tailored for data warehousing and analytical tasks.

Distribution

Distribution in Azure SQL Server refers to how data is organized and spread across different physical or virtual servers for efficient data storage and retrieval. Azure SQL offers several distribution methods to optimize query performance, manage workloads, and improve availability.

Types of Distribution

Round Robin Distribution

Type: Data is evenly distributed across multiple servers in a circular manner. Each piece of data is sent to the next server in line.

Usage: Suitable for scenarios with unpredictable data access patterns or when the goal is to evenly distribute workloads. However, it's less effective when data locality is crucial for performance.

Hash Distribution

Type: Data is distributed based on the hash value of a specific column or a combination of columns. Rows with the same hash value are sent to the same server.

Usage: Ideal when ensuring data locality for queries, or when data access patterns are predictable. Common in data warehousing scenarios where specific queries benefit from localized data storage.

Replica Distribution

Type: Not a traditional distribution method, but involves creating replicas of data across servers to ensure high availability and redundancy. Replicas can be distributed using round robin or hash distribution.

Usage: Essential for ensuring high availability and fault tolerance, commonly used when data consistency and reliability are top priorities.

SQL Services

Azure offers multiple options for running SQL Server workloads, each tailored to different levels of control, management, and scalability. The key services are SQL Managed Instance, SQL Virtual Machine, and SQL Database.

SQL Managed Instance

SQL Managed Instance is a fully managed SQL Server service designed to provide near 100% compatibility with on-premises SQL Server. It offers automatic patching, backup, high availability, and scalability without the need to manage hardware or the operating system.

Usage: Ideal for migrating existing SQL Server applications to Azure or when you need a fully managed SQL Server environment that is highly compatible with on-premises setups.

SQL Virtual Machine

SQL Virtual Machine provides a virtual machine where you can install and manage SQL Server. You have full control over the VM and SQL Server configurations, but you must manage operating system updates, backup, and high availability yourself.

Usage: Suitable for custom configurations, legacy applications, or when you need complete control over the environment and SQL Server setup.

SQL Database

SQL Database is a fully managed Platform-as-a-Service (PaaS) offering for SQL Server. It requires no server or VM management and scales easily with minimal administrative overhead.

Usage: Best suited for new cloud-native applications, microservices, or scenarios where you need a serverless, fully managed database with easy scalability and minimal management.

Choosing the Right Azure SQL Service

The choice between SQL Managed Instance, SQL Virtual Machine, and SQL Database depends on the specific needs of your application:

• SQL Managed Instance: Ideal when you need a balance of control and management, especially for migrating existing SQL Server workloads to Azure.
• SQL Virtual Machine: Suitable for scenarios where you need complete control over the environment, custom configurations, or need to support legacy applications.
• SQL Database: The best option for cloud-native applications and microservices, offering ease of scalability and minimal maintenance overhead.