When and How to Update Statistics in Azure SQL Database

Accurate statistics are a cornerstone of good query performance in Azure SQL Database. While the platform automatically manages statistics in most scenarios, there are real‑world cases where manual intervention is not only recommended—but essential. This article explains when, why, and how to update statistics in Azure SQL Database, with practical samples and real customer scenarios drawn from production support cases.

Microsoft Learn reference (overview): Why statistics matter sql Server’s query optimizer relies on statistics to estimate row counts, choose join strategies, allocate memory grants, and decide whether to run operations in parallel. When statistics are stale or inaccurate, even well‑indexed queries can suddenly degrade. In Azure SQL Database: * AUTO_CREATE_STATISTICS is enabled and managed by the platform * AUTO_UPDATE_STATISTICS runs asynchronously Because updates are async, queries may continue running with outdated cardinality estimates until statistics refresh completes.

When manual statistics updates are required 1. After large data changes (ETL / BATCH OPERATIONS) Customer scenario A nightly ETL job bulk‑inserts millions of rows into a fact table. The following morning, reports time out and logical reads spike.

Why it happens Auto‑update thresholds are based on row‑count changes and may not trigger immediately—especially for append‑only or skewed data. Recommended action UPDATE STATISTICS dbo..