Azure SQL Database

Deployment Options

Purchasing Models

DTU Model (Database Transaction Units)

A bundled measure of compute, memory, and I/O. Simpler but less transparent. Three tiers: Basic, Standard, Premium.

vCore Model (Recommended)

Choose specific number of vCPUs, memory, and storage independently. More transparent pricing. Supports Azure Hybrid Benefit. Five tiers: General Purpose, Business Critical, Hyperscale, Serverless, and Free offer.

Service Tiers (vCore)

Elastic Pools

Elastic Pools allow multiple databases to share a pool of compute and storage resources. Instead of provisioning maximum resources for each database (that each uses at different times), they share the pool — reducing overall cost.

Serverless Tier

Serverless Azure SQL Database auto-scales compute between a configured min and max, and automatically pauses the database after a period of inactivity — billing stops for compute while paused (storage charges continue). Perfect for development, testing, or applications with infrequent usage.

• Auto-pause delay: 1 hour minimum, up to 7 days
• First query after pause has a "cold start" delay (~30 seconds)
• Not suitable for workloads requiring 24/7 availability

Active Geo-Replication

Active Geo-Replication creates up to 4 readable secondary databases in different regions. Secondaries are continuously synchronised (asynchronously). For disaster recovery — if the primary region fails, you can manually failover to a secondary. Secondaries can also handle read workloads to offload the primary.

Auto-Failover Groups

Auto-Failover Groups build on geo-replication and add automatic failover — if the primary becomes unavailable, Azure automatically fails over to the secondary. A single connection string is provided that always points to the current primary — your application doesn't need to change anything.

Automated Backups and PITR

Azure SQL Database automatically takes:

• Full backups — Weekly
• Differential backups — Every 12 hours
• Transaction log backups — Every 5–10 minutes

Point-in-time restore (PITR) — Restore to any point within the retention period. Default retention: 7 days. Configurable: 1–35 days.

Security Features

• Transparent Data Encryption (TDE) — Encrypts data at rest automatically (enabled by default)
• Always Encrypted — Column-level encryption; data is encrypted even from the database engine's perspective
• Row-Level Security (RLS) — Filter rows based on user identity
• Dynamic Data Masking — Mask sensitive data for non-privileged users (e.g., show only last 4 digits of phone numbers)
• Azure AD Authentication — Authenticate with Azure AD identities instead of SQL logins
• Advanced Threat Protection — Detect unusual access patterns (SQL injection attempts, anomalous access)
• Firewall Rules — Control which IPs can connect; Private Endpoint for no public access

Connecting to Azure SQL Database

Azure SQL Database uses port 1433. Connection string format:

Server=tcp:myserver.database.windows.net,1433;
Initial Catalog=mydatabase;
Persist Security Info=False;
User ID=myuser;
Password=mypassword;
Encrypt=True;
TrustServerCertificate=False;

Creating via CLI

# Create a logical SQL server
az sql server create \
  --name mydbserver-2026 \
  --resource-group myRG \
  --location centralindia \
  --admin-user sqladmin \
  --admin-password "SecureP@ssword123!"

# Create a database (General Purpose, 2 vCores)
az sql db create \
  --resource-group myRG \
  --server mydbserver-2026 \
  --name myDatabase \
  --edition GeneralPurpose \
  --compute-model Provisioned \
  --family Gen5 \
  --capacity 2

# Allow Azure services to connect (optional)
az sql server firewall-rule create \
  --resource-group myRG \
  --server mydbserver-2026 \
  --name AllowAzureServices \
  --start-ip-address 0.0.0.0 \
  --end-ip-address 0.0.0.0