Query Optimization
A collection of 72 issues
Teradata 16 Introduces New Features for UNION ALL Queries
Teradata UNION ALL - The New Features of Release 16
Teradata 16 introduces new features for UNION ALL queries that can enhance their performance, although their application is not guaranteed.
The Optimizer will opt for executing the query through conventional methods if the cost estimations for the traditional execution plan
How to Join Partitioned Tables with an Unusual Trick for Improved Performance
Learn an unusual trick to improve the performance of joining partitioned tables with different primary indexes or partitioning. Read on to find out more.
Teradata Statistics Extrapolation: What it is and How it Works
Learn about Teradata Statistics Extrapolation, a technique that allows for reasonable estimations when querying historical data with stale statistics.
Simplify Teradata Development: Avoiding the Pitfalls of Over-Specialization and Large SQL Statements
Learn how specialization in Teradata development can lead to the development of huge SQL statements and how to reduce the risk of bad performance.
A Comprehensive Guide to Teradata Statistics: Common Misconceptions, Best Practices, and Real Reasons Behind Performance Degradation
Learn the truth about Teradata statistics and their impact on system performance. Address common misconceptions, follow best practices, and optimize your system for peak performance.
Introduction to Teradata Nested Join: The Cheapest Join Method Using Indexes
Learn about the Teradata Nested Join, the cheapest join method using indexes. We explore its prerequisites, variants, and performance.
Improving Row Estimates with Teradata Check Constraints
Without Teradata CHECK Constraint
When a non-indexed column is utilized in a retrieval operation (i.e. WHERE statement) and lacks Teradata Check Constraints, the Optimizer employs heuristics to approximate the number of rows in the resulting set by inferring missing statistics.
The estimated number of rows is 7,342, equivalent
Optimizing Join and Aggregation with Teradata UNION ALL Views
Teradata 16 introduces a new option for handling sets of rows combined with "UNION ALL" in views and derived tables, reducing resource usage. The optimizer can apply aggregation steps and join operations to each branch of the "UNION ALL" separately, resulting in smaller spool sizes and improved perf
Teradata Heuristics for Nonindexed Columns
Learn about heuristics in Teradata optimizer and how they estimate the number of selected data rows for nonindexed columns in WHERE condition predicates. This post analyzes several queries and their estimates based on heuristics and provides insights on how to replace heuristic estimations with more