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322 technical articles on Teradata, Snowflake, Databricks, SQL tuning and data warehouse architecture — written from production experience, not vendor decks.

Filter efficiently with Teradata NOS

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Teradata NOS facilitates querying data in an S3 object store with ease. To attain maximum performance, partitioning external data is crucial for efficient reading. This article outlines the key considerations for optimal efficiency when reading data from the object store. To begin, we must establish S3 access by obtaining an AUTHORIZATION object. In this instance, …

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Date ranges and business calendars beyond recursion and Teradata SYS_CALENDAR

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In a previous article, Roland explained how to use recursion to build a data range without touching a physical table. This time, we explore an alternative approach that avoids recursion at the expense of single-AMP, single-row access. We can use this approach to build both a wide date range as well as a narrow one. We …

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Teradata strtok_split_to_table, CSVLD, Unpack: Column Splitting in Teradata

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Splitting column content can be a challenging task. Teradata provides multiple methods to achieve this, each with unique pros and cons. In this article, we will examine these techniques in detail. To begin, we will generate a table containing sufficient random data to assess every option’s efficiency and resource utilization. The Teradata “CSVLD” Function This …

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Comparing Index Types of SQL Server and Teradata: Clustered vs Row Partitioning, Non-clustered vs NUSI, USI, Join Index, and More

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This article compares the index types in SQL Server and Teradata. It can benefit those transitioning between the two platforms to understand their distinctions and overlaps, despite their different architectures. Clustered Index vs Teradata Row Partitioning The SQL Server’s clustered index arranges table rows in a specific physical order, making it ideal for range-based queries. …

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A Beginner’s Guide to Teradata Multiload and Fastload Widely read

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Introduction to Teradata Multiload and Fastload MultiLoad does not run in isolation: how the utilities are throttled as a workload of their own and the smaller-volume alternative in BTEQ.

How the Number of Rows per Data Block Affects Teradata NUSI Selectivity: A Case Study

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Teradata NUSI Selectivity and Data-Block Density The goal of this article is to show how the number of rows per base-table data block impacts the selectivity threshold for Non-Unique Secondary Indexes (NUSI) in Teradata. Understanding this correlation is critical when analyzing query plans and tuning indexing strategies.The number of qualifying rows that make a NUSI …

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Understanding Teradata Statistics Histograms: How the Optimizer Estimates Cardinality for WHERE Conditions

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Teradata Statistics Histograms – A Short Introduction Many are familiar with the Optimizer’s statistical confidence levels. I was recently surprised to discover that a “high confidence” rating does not guarantee a fully accurate estimation (provided the statistics collected are not stale). While I remain hopeful that my observations may be attributed to a bug, I wanted …

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Hadoop and Teradata Data Warehousing: A Comparison and Integration Perspective

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Hadoop is a buzzword in the world of big data, but its actual value can be concealed by the hype. This article compares Teradata and Hadoop Data Warehousing, highlighting the advantages of leveraging Hadoop’s scalability and preprocessing capabilities to improve Teradata’s performance. However, the implementation of Hadoop by big database vendors may not be fully functional, and companies should proceed with caution before adopting new technologies.

A Teradata HASHROW Table Difference Screening Test

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Have you ever experienced extended waiting times for a table comparison to yield results? Have you ever been compelled to halt and defer quality checks on sizable tables owing to excessive resource utilization during a previous attempt? What if you possessed a straightforward screening test indicating which tables require further examination from a huge array …

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