面试题与答案

Primary Index is used for distributing data across the AMPs (Access Module Processors) in a Teradata system. It determines the distribution of rows in a table based on the primary index value.

Example:

SET tables in Teradata eliminate duplicate rows, ensuring that each row is unique. They are useful in scenarios where you want to store distinct values.

Example:

The COLLECT STATISTICS statement is used to gather statistics on columns or indexes in a Teradata table. It helps the query optimizer make better decisions for query execution plans.

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INNER JOIN returns only the matching rows from both tables, while LEFT JOIN returns all rows from the left table and the matching rows from the right table.

Example:

The PARTITION BY clause in Teradata is used in window functions to divide the result set into partitions to which the window function is applied separately. It is commonly used with functions like ROW_NUMBER() and RANK().

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The PRIMARY KEY constraint in Teradata is used to uniquely identify each row in a table. It ensures that the values in the specified columns are unique and not NULL.

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Teradata provides various aggregate functions like SUM, AVG, MIN, MAX, and COUNT to perform calculations on a set of values. These functions are commonly used in SELECT queries for summarizing data.

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Vantage is the modern analytics platform from Teradata that integrates data analytics, data lakes, and data warehouses. It allows users to analyze and derive insights from data stored in different environments.

The LOCKING modifier in Teradata is used to specify the type of locks to be used during a query. It allows users to control the level of concurrency and the type of locks acquired on tables.

Example:

INDEX constraints in Teradata define the indexes on tables, specifying how data is physically organized. They are crucial for optimizing query performance by allowing the database to locate and retrieve data more efficiently.