327 technical articles on Teradata, Snowflake, Databricks, SQL tuning and data warehouse architecture — written from production experience, not vendor decks.
Learn the access requirements and variants of Teradata nested joins. Indexed lookups can help selective workloads, but costs and AMP participation vary.
What is the Teradata Sample Function? The SAMPLE function returns a set of randomly selected rows. Here are the characteristics: The Syntax of the Sample Function SAMPLE [WITH REPLACEMENT] [RANDOMIZED ALLOCATION][WHEN <condition> THEN] {<number of row> | <percentage>} […,<number-of-rows> | <percentage>][ELSE {<number of rows> | <percentage } END] Here are some examples of how to …
Fast Path INSERT/SELECT efficiently loads a single table. Requirements for Teradata Fast Path INSERT /SELECT How does the Fast Path INSERT/SELECT work? This reduces access to mass storage (such as hard disk or solid-state disk). The process involves generating complete data blocks on every AMP and subsequently transferring them to mass storage using a single …
A hot standby node belongs to a clique of nodes and does not host virtual processes such as AMPs or Parsing Engines. The standby node remains idle until a member of its clique crashes or fails. At this point, the standby node is activated to take over the failed node’s responsibilities. Failover may move AMPs …
Skewed Teradata Joins – The Initial Situation Consider the scenario where one table includes various currencies while the other comprises customers’ accounts with their corresponding currency. Essentially, the ISO code of the currency serves as a foreign key in the account table. CUSTOMER TABLE CUSTOMER_ID CUSTOMER_NAME CURRENCY_CD 1 Nina Lowery EUR 2 Alexia Neal USD …
Learn how Teradata Integrated Workload Management assigns workloads to queries and offers features like filters and throttles to improve system performance.
Teradata sparse maps place small tables on one or a few AMPs. Learn how map choice, table placement and workload affect access and performance.
Learn about the Teradata row size limits and how to deal with the “3577 Row size or Sort Key size overflow” error in this informative article.
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 a single AMP is best …
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 performance.
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