Azure DP-900 Short Notes: Explore relational data services in Azure
Tags: azure, cloud, dp900, certification
Published: 2021-02-17 04:10:59

👉Learn Module: [Explore relational data services in Azure](https://docs.microsoft.com/en-us/learn/modules/explore-relational-data-offerings/)
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## Introduction

👉Database(DB) is a collection of data.

👉Data can be structured, semi-structured or unstructured.

👉Two types of DB

1. Relational DB - Holds structured data.
2. Non-Relational DB - Holds semi-structured or unstructured data.

👉On-premise DB = High infrastructure cost | Solution = Migrate to cloud.

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## Explore relational Azure data services

👉Three common cloud offering models.

1. Infrastructure-as-a-Service(IaaS)

     👉Creating Virtual infrastructure in the cloud just as on premise. 

    👉Same as on-premise except you do not have to buy and maintain the hardware.

    Ex: Azure Virtual Network

2. Platform-as-a-service(PaaS)

    👉 Azure creates virtual infrastructure in cloud

    👉Customer responsible for installing and managing software.

    👉Can easily scale up and down.

    Ex: Azure SQL Databases

3. Software-as-a-Service(SaaS)

    👉specific software packages that runs on the cloud

    Ex: Office 365

👉Azure Data Services = PaaS based DBMS service manage by Microsoft.

Ex: Azure Database for MySQL servers , Azure Database for MariaDB servers, Azure Database for PostgreSQL

👉Advantages of Azure Data Services

- Reduce DB administration workload.
- SLA = 99.99%

👉Disadvantages of Azure Data Services

- Custom DB scripts restricted (Ensure security)
- Lack of full DBMS features (Ensure security)

👉 Base price = infrastructure charges+ licensing charges + administration charges.

👉 Designed to be always on. 

👉 Capital Expenditure & Administrative Effort in running DB .

 Physical(On-Premise DB)  > IaaS(DB on Azure VM)  > PaaS (Azure SQL database)

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## SQL Server on Azure virtual machines

👉IaaS offering to run SQL Server in cloud.

👉No on-premises hardware to manage.

👉lift-and-shift ready  = Move a database directly from on-premise server to VM on the cloud and configure any app connecting to on-premise database server to connect to the VM hosting the database server in the cloud.

👉Advantages

- Create hybrid environment where operation running are shared with both on-premise and the cloud.
- lift-and-shift ready.
- Create test environment without buying on-premise new hardware.
- Scale up and down without reinstalling software.

## Azure SQL Database

👉PaaS offering.

👉There are three differ options
- Single Database
- Elastic pool
- Managed Database
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1.Single Database

👉a single SQL Server database.

👉By default, resources are pre-allocated.

👉Charged per hour for the resources you've requested.

👉Optional server-less configuration.
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2.Elastic pool

👉Multiple databases can share the same resources.

👉Pool = resources

👉Your DBs only access the pool.

👉Suitable for databases with resource requirements that vary over time.

👉Data Migration Assistant (DMA) helps to check on-premise DB environment compatibility with Azure SQL Database and reports issues and  and recommendations.

Advantages

👉scalability

👉Automatic updates and patches.

👉High Availability (99.99% SLA)

👉Advanced threat protection

👉Auditing

👉Encryption

**Important —>linked servers used to perform distributed queries are not supported by single elastic pool options.
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3.Managed instances

👉Same as Single Database or Elastic Pool with administrative features available to SQL Server.

👉A fully controllable instance of SQL Server in the cloud.

👉All advantages of option 1 and 2 and 

1. Full control over security and resource allocation for your databases 
2. Do not have to manage VMS(On-premise option).
3. 100% compatibility with SQL Server Enterprise Edition, running on-premises.

👉Depend on other azure resources such as Azure Storage for backups to provide security and supportability features.

**Additional features (Not available in other 2 options) - > linked servers, Service Broker, DB Mail