322 technical articles on Teradata, Snowflake, Databricks, SQL tuning and data warehouse architecture — written from production experience, not vendor decks.
What is a Teradata Macro? The Teradata macro executes multiple SQL queries in a single transaction, ensuring that all requests are successful or changes to database objects are rolled back. What are the Features of Teradata Macros? How is a Macro created? How is a Macro changed? How is a Macro dropped? How is a …
What is the Waterfall Model? The waterfall model facilitates the sequential progression of a data warehouse project. Each phase must be concluded before the subsequent stage commences. The following stages will be navigated: What are the Problems with the Waterfall Model? Typically, these issues are identified solely during the verification stage of testing. Why do …
Introduction to Teradata Sample Statistics Discover the optimal utilization of Teradata Sample Statistics, including when, how, and why to implement them. Sample statistics require columns with a high degree of diversity in values. A UPI satisfies this criterion, and only columns with numerous unique values should be considered for collecting sample statistics for the NUPI. …
Introduction to Teradata Referential Integrity Teradata implements 3 Types of Referential Integrity. 1. What is Standard Referential Integrity? The Standard Referential Integrity checks every Row INSERT, DELETE, or UPDATE immediately to ensure referential integrity. A reference index sub-table is required for referential integrity. Violation of referential integrity results in the failure of execution and generates …
Teradata Sessions explained in a few Sentences Example 1: Multiple Sessions which do not improve performance The graph shows that all four transactions (T1, T2, T3, T4) are concurrently active on all AMPs. Even for a single-row lookup, these transactions necessitate accessing all AMPs. None of the transactions use a single rowhash for access, resulting …
Teradata Table Design Checklist As creating tables is a frequent task, I deemed it necessary to provide a checklist. 1. Primary Index Or NOPI Table? The Primary Index serves multiple purposes, primarily functioning as the primary access path to the data and being optimized for an even distribution of rows. However, designing a table without …
Teradata Query Parallelism A query on a Teradata system runs in parallel at every step, whether for joining, sorting, or aggregating data. Teradata’s uniqueness lies in its ability to apply parallelism at every step of the query process. This advantage resulted from its architectural design, which integrated high levels of parallelism from the start, even …
What are Teradata Surrogate Keys? A Teradata Surrogate Key is an artificial key that maps to a natural key. It is usually of the data type INTEGER or BIGINT and is represented by a single column. The natural key can consist of multiple columns. The surrogate key is generated automatically and is represented by an …
Have you observed the different behavior of the Teradata LIKE operator when applied to a CHAR or VARCHAR data type column? Consider the following table as an illustration: Creating a table: To illustrate, we will add a single row. We will run the SQL statement for the column with the VARCHAR data type. Next, we …
Teradata SQL and Advanced GROUPING Functions The advanced GROUPING functions will be demonstrated through the following example. The foundation of this demonstration is a table consisting of the flight count for each aircraft and date: CREATE MULTISET TABLE Flights ( PLANE AS BIGINT NOT NULL, FLIGHTDATE AS DATE NOT NULL, NR_FLIGHTS INTEGER NOT NULL ) …
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