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SQL

A collection of 180 issues

Teradata Data Access: Single-AMP vs. All-AMP Binary Search and Sequential Search

Teradata data access is categorized based on the number of AMPs involved and the technique employed to search rows within a data block. In our article about SQL Tuning, we mentioned that one of the main goals in performance optimization is to distribute the workload evenly across all AMPs. Using

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

Understanding Soft Referential Integrity and Its Role in Improving Performance

Learn about referential integrity and how it ensures data consistency in databases. Discover soft referential integrity and its use in inner join elimination.

How to Optimize Joins in Teradata: A Case Study

Learn how to optimize joins in Teradata with this case study. Discover how simple changes in query text can improve query performance.

How to Use Biased Value Histograms for Accurate Statistics Estimation on Teradata SQL

Learn how biased value histograms store exact cardinalities and provide up-to-date statistics for queries, and witness how the Optimizer estimates the number of rows for a given query.

Improving Performance through Query Rewriting with Row Partition Elimination: A Real-World Optimization Example on a 400-Million-Row Table

Learn how query rewriting can improve performance in row partition elimination. Follow the test setup to optimize the retrieval of rows from a table.

How to Reduce Skew in Teradata Joins Using the RANDOM() Function

Teradata Tuning Ideas: Best Practices and Strategies

Learn how to optimize Teradata performance with these general tuning ideas. From changing one parameter at a time to testing on the target system.

Practical Approach for Teradata SQL Tuning: Finding the Root Cause of Performance Issues