Articles

Page 7 of 11 — showing articles 109 to 126 of 183

Incorrect Results with Merge Join

Descending

A detailed analysis of a SQL Server optimizer bug that causes incorrect results when a descending non-unique index exists on a partitioned table.

Two Partitioning Peculiarities

Peculiar Partitions

Join and group by clauses may need to be written in a specific way to get the best results from the SQL Server query optimizer when using partitioning.

Aggregates and Partitioning

Aggregating and Partitioning

Improving performance for SQL Server MIN and MAX queries on partitioned tables and working around query optimizer limitations.

Optimizer Limitations with Filtered Indexes

Filtered

SQL Server filtered unique indexes do not provide uniqueness information to the query optimizer. Redundant predicates may be needed to match filtered indexes.

The Problem with Window Functions and Views

A Gloomy Window

The SQL Server query optimizer can fail to push a filter past a windowing function. This article shows how to improve the performance of queries that filter on views with window functions like ROW_NUMBER and RANK.

The Halloween Problem—Part 4

Halloween 4

SQL Server Halloween Protection and the query optimizer. Redundant sorts and other non-eager table spool options.

The Halloween Problem—Part 3

Halloween 3

SQL Server Halloween Protection special optimizations for the MERGE statement. Hole-filling and rowset sharing.

The Halloween Problem—Part 2

Halloween 2

When SQL Server Halloween Protection is needed for INSERT and DELETE statements. Constraint checking and phase separation.

The Halloween Problem—Part 1

Halloween 1

Halloween Protection for SQL Server UPDATE queries. Why protection is needed and how it is implemented.