Teradata For Beginner 4 — Questions and Answers
Question 1: In Teradata, what is a Secondary Index (SI) used for?
- To redistribute data to different AMPs
- To provide an alternative access path to rows without changing data distribution (Correct answer)
- To enforce referential integrity between tables
- To compress column data on disk
Correct answer: To provide an alternative access path to rows without changing data distribution
A Secondary Index creates a subtable that provides an alternative lookup path without changing where the actual rows are stored.
Question 2: Which Teradata command collects statistical data about table columns to help the optimizer?
- ANALYZE TABLE
- COLLECT STATISTICS (Correct answer)
- UPDATE STATS
- REBUILD INDEX
Correct answer: COLLECT STATISTICS
COLLECT STATISTICS gathers demographic data about column values and stores it so the query optimizer can build better execution plans.
Question 3: What is the BYNET in Teradata architecture?
- A backup network for disaster recovery
- The high-speed interconnect network between nodes that carries all inter-AMP communication (Correct answer)
- A network protocol for loading data from external sources
- A virtual private network for Teradata sessions
Correct answer: The high-speed interconnect network between nodes that carries all inter-AMP communication
BYNET is Teradata's proprietary high-bandwidth, fault-tolerant interconnect that enables fast communication and data transfer between all nodes.
Question 4: Which of the following best describes a Unique Primary Index (UPI) in Teradata?
- It allows duplicate values but distributes data evenly
- It guarantees uniqueness and routes each row to exactly one AMP (Correct answer)
- It creates an automatic clustered index on disk
- It is required for all Teradata tables
Correct answer: It guarantees uniqueness and routes each row to exactly one AMP
A UPI enforces uniqueness on the indexed column(s) and ensures each unique value hashes to a single, specific AMP.
Question 5: What does the COALESCE function do in Teradata SQL?
- Concatenates multiple strings into one
- Returns the first non-NULL value from a list of expressions (Correct answer)
- Converts data types automatically
- Rounds numeric values to a specified precision
Correct answer: Returns the first non-NULL value from a list of expressions
COALESCE evaluates its arguments in order and returns the first expression that is not NULL.
Question 6: In Teradata, what is the purpose of the Transient Journal?
- To log all DDL changes for auditing
- To store before-images of changed rows for rollback in case of a transaction failure (Correct answer)
- To track user login and logout activity
- To temporarily hold data being loaded by FastLoad
Correct answer: To store before-images of changed rows for rollback in case of a transaction failure
The Transient Journal holds before-images of modified rows so that if a transaction fails or is rolled back, the original data can be restored.
Question 7: Which Teradata feature allows you to query a table as it existed at a previous point in time?
- Flashback Query
- Temporal Query / AS OF (Correct answer)
- Time Travel
- Snapshot Isolation
Correct answer: Temporal Query / AS OF
Teradata's temporal tables and the AS OF clause allow you to query historical data as it existed at a specific point in time.
Teradata For Beginner 4
In Teradata, what is a Secondary Index (SI) used for?