LAG in SQL Server - Examples & AI Generator

The LAG function in SQL Server lets you compare values from previous rows within a query, unlocking trends and sequential analyses. But the correct SQL Server LAG syntax can be tough to remember—especially since it differs from other databases and quickly gets complex with multiple OVER clauses or business needs. AI2sql removes the trial-and-error: you describe your reporting need, and it generates production-ready queries in 10 seconds—no coding or syntax recall required.

LAG Syntax in SQL Server

Basic Structure

LAG (scalar_expression [,offset] [,default])
    OVER ( [PARTITION BY partition_expression] ORDER BY order_expression )

• scalar_expression: Column to retrieve the lag value from.

• offset: (Optional) Number of rows behind to look. Default is 1.

• default: (Optional) Value if LAG goes past the first row.

• PARTITION BY: (Optional) Defines grouping—unique to SQL Server’s T-SQL.

This syntax is specific to SQL Server and may not match MySQL or PostgreSQL—making it important for cross-platform developers to check details.

LAG Examples You Can Generate Instantly

Copy, tweak, or generate your own with AI2sql (no coding required):

• Example 1: Compare each customer order total to their previous order

  SELECT
    CustomerID,
    OrderDate,
    TotalAmount,
    LAG(TotalAmount, 1, 0) OVER (PARTITION BY CustomerID ORDER BY OrderDate) AS PrevOrderAmount
  FROM
    Orders;
  
  

• Example 2: Calculate day-to-day sales difference for a product

  SELECT
    ProductID,
    SaleDate,
    UnitsSold,
    UnitsSold - LAG(UnitsSold) OVER (PARTITION BY ProductID ORDER BY SaleDate) AS UnitsDifference
  FROM
    ProductSales;
  
  

• Example 3: Show revenue change by month sitewide

  SELECT
    FORMAT(OrderDate, 'yyyy-MM') AS OrderMonth,
    SUM(TotalAmount) AS MonthlyRevenue,
    SUM(TotalAmount) - LAG(SUM(TotalAmount)) OVER (ORDER BY FORMAT(OrderDate, 'yyyy-MM')) AS RevenueChange
  FROM
    Orders
  GROUP BY
    FORMAT(OrderDate, 'yyyy-MM');
  
  

Generate LAG queries in 10 seconds with AI2sql—just describe your business logic and get instant, copy‑ready SQL for SQL Server.

Why Use AI2sql Instead of Manual LAG Coding

• No manual syntax lookup: Skip SQL Server documentation or StackOverflow.

• Instant adaptation: AI2sql knows SQL Server nuances (partitioning, date formats, window ordering).

• Faster workflows: Production‑ready queries for analytics or engineering—in 10 seconds.

• Trusted by 50,000+ users in 80+ countries.

Try AI2sql Generator or Learn LAG in more detail.

FAQ: LAG in SQL Server

• Can I use LAG without PARTITION BY?
  Yes. The PARTITION BY clause is optional. If omitted, LAG computes over the entire result set based on your ORDER BY clause.

• Is LAG available in all versions of SQL Server?
  

  LAG is supported from SQL Server 2012 and later.

• Is the LAG syntax the same in MySQL and PostgreSQL?
  No. There are subtle differences in window function implementation, especially around OVER() clauses and default handling.

Conclusion: Don’t waste time writing out and debugging complex LAG logic. With AI2sql, describe your reporting goal—in plain English—and get production‑ready SQL Server LAG syntax for real business scenarios, instantly. Generate Your First Query Now.