The Problem with Window Functions and Views

Introduction

Since their introduction in SQL Server 2005, window functions like ROW_NUMBER and RANK have proven to be extremely useful in solving a wide variety of common T-SQL problems. In an attempt to generalize such solutions, database designers often look to incorporate them into views to promote code encapsulation and reuse.

Unfortunately, a limitation in the SQL Server query optimizer often means that views¹ containing window functions do not perform as well as expected. This post works through an illustrative example of the problem, details the reasons, and provides a number of workarounds.

Note: The limitation described here was first fixed in SQL Server 2017 CU 30. Optimizer fixes must be enabled using trace flag 4199 or the database scoped configuration option. The fix is standard behaviour without optimizer hotfixes under compatibility level 160 (SQL Server 2022).