Azure SQL Database

Azure SQL Database is a fully managed relational database service built on the Microsoft SQL Server engine. It handles infrastructure management — including patching, backups, monitoring, and high availability — so that you can focus on application development and query optimisation.

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Deployment Models

Single Database

A standalone database with dedicated compute and storage resources. Each database is isolated and managed independently.

az sql db create \
  --resource-group rg-demo \
  --server my-sql-server \
  --name my-database \
  --service-objective GP_Gen5_2

Elastic Pool

Multiple databases sharing a pool of compute resources (eDTUs or vCores). This is ideal when you have many databases with unpredictable or variable usage patterns — some databases are busy while others are idle.

az sql elastic-pool create \
  --resource-group rg-demo \
  --server my-sql-server \
  --name my-pool \
  --edition GeneralPurpose \
  --capacity 4

A single elastic pool can hold up to 500 databases. Each database can burst up to the pool's total resources while the overall cost remains capped.

Serverless Compute Tier

A compute tier within the single database model that auto-scales and auto-pauses:

Feature	Description
Auto-scaling	vCores scale between a configured min and max based on demand
Auto-pause	The database pauses after a configurable idle period (no compute cost while paused)
Resume	Automatically resumes on the next connection attempt
Billing	Per-second billing for compute; storage is always billed

Serverless is ideal for development, testing, and applications with intermittent, unpredictable workloads.

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Purchasing Models

vCore Model

Choose virtual cores, memory, and storage independently:

Component	You Choose
vCores	Number of virtual cores (2, 4, 8, 16, ...)
Memory	Determined by vCore count
Storage	Up to 4 TB (General Purpose) or 100 TB (Hyperscale)
Hardware	Gen5, Fsv2, DC-series

The vCore model supports Azure Hybrid Benefit, allowing you to reuse existing SQL Server licences for up to 55% savings.

DTU Model

A bundled measure of compute, storage, and I/O resources:

Tier	DTU Range	Max Storage
Basic	5 DTUs	2 GB
Standard	10–3000 DTUs	1 TB
Premium	125–4000 DTUs	4 TB

DTUs are simpler for predictable workloads where you do not need fine-grained control.

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Service Tiers

General Purpose

The default tier for most workloads:

• Balanced compute and storage
• Remote storage (Azure Premium Storage)
• 99.99% SLA
• Zone-redundant option for higher availability (99.995% SLA)
• Supports both vCore and DTU models

Business Critical

For low-latency, high-transaction workloads:

• Local SSD storage (lower latency than General Purpose)
• Built-in read replica (one free read-only replica)
• In-memory OLTP (in-memory tables and columnstore)
• 99.99% SLA (99.995% with zone redundancy)

Hyperscale

For very large databases and rapid scaling:

• Supports databases up to 100 TB
• Near-instant backups (snapshot-based, regardless of database size)
• Rapid scale-out with up to 4 named read replicas
• Fast database restore (minutes, not hours)
• Decoupled storage and compute architecture

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Key Features

Automatic Backups

Azure SQL Database takes automatic backups without any configuration: