Top Teradata Interview Questions & Answers

What Is Teradata? 

Teradata is a relational database management system ideal for large-scale data warehousing applications. This open-source system works on the concept of parallelism, allowing simultaneous execution of multiple data warehouse operations. It can run on UNIX, Windows, Linux, and Mac OS. 

Teradata enhances the performance of organizations by efficiently managing large data warehouse operations and helping them fulfill their high-impact business goals. This tool is the choice of hundreds of companies worldwide for Business Intelligence and Enterprise Data Warehousing.   

Teradata Interview Questions for Freshers

1. State the importance of using Teradata. 

The following reasons make Teradata important: 

• The system can store, process, and handle large volumes of data (over 50 petabytes).  
• It can easily be integrated with various business intelligence tools.  
• It supports OLAP (online analytical processing) for performing complex data analytics.  
• The software offers hardware-based and cloud-based data warehousing. 
• It supports Structured Query Language (SQL) for interacting with data stored in tables. 
• Based on Massive Parallel Processing (MPP), Teradata can run multiple tasks simultaneously, providing fast processing speeds.

2. Explain the newly developed features of Teradata.

Source: InterviewBit

• Unlimited Parallelism: Based on Massive Parallel Processing (MPP), Teradata divides large data processing tasks into smaller ones and runs them in parallel.   
• Shared Nothing Architecture: The disks, AMPs, and Teradata nodes are independent. They don't share resources with others and thus provide optimized performance for various tasks. 
• Linear Scalability: The system is linearly scalable to handle large volumes of data efficiently.   
• Connectivity: It can connect with channel-attached systems, including networks and mainframes.  
• Mature Optimizer: It provides methods for retrieving the data via SQL query and can handle up to 64 joins per SQL query.  
• Robust Utilities: Provides utilities for exporting and importing data to and from Teradata systems like Fastexport, Fastload, Multiload, TPT, and more.    
• Load and Unload utilities: Allow users to move data in and out of Teradata systems. 
• Automatic Distribution: Automatically distributes data evenly in disks without manual intervention.  
• Low TCO (Total cost of ownership): Easy setup, administration, and maintenance.  

3. Explain Teradata Architecture.

Source: InterviewBit

Based on MPP, Teradata's architecture can be divided into two parts: storage architectures comprising parsing engine & BYNET and retrieval architectures comprising AMPs & disks.

Parsing Engine (PE): Receives client queries and prepares execution plans to execute SQL queries. When the user executes a SQL query, it is connected to the PE, which carries out the following functions: 

• Check if the queries have syntax errors. 
• Determines whether the objects in the SQL query exist or not. 
• Prepares query execution plans and then sends them to BYNET. 
• Receives SQL query results from the AMPs and sends them to the client.

Access Module Processors (AMPs): The virtual processor connected to PE via BYNET. Each AMP has its disk for reading and writing data. Once AMPs receive the data and execution plan from the PE, it performs data type conversion, filtering, aggregation, and sorting. It further writes (stores) data to the relevant disks. Whenever a query is fired, all AMPs work together to provide the data. 

BYNETs: The communication channel between PEs and AMPs. It receives the execution plan from the PE and forwards it to the AMPs. Teradata has two BYNETs: BYNET 0 and BYNET 1. So, the second BYNET takes over when the first one fails. Also, both can be made functional when large data volumes are being dealt with. 

Disks: Teradata offers virtual disks for each AMP that serves as a storage area for each AMP. 

4. What are the different string manipulation functions and operators in Teradata?

Teradata String functions help manipulate strings. They are compatible with the ANSI standard. The different string functions are: 

• SUBSTRING: Extracts a particular portion of the long string (ANSI standard).

Example:

Consider a string “Simplilearn” from a table.

SELECT SUBSTRING('Simplilearn' FROM 1 FOR 5);

Output: 

Inter

• POSITION: Locates an individual character in a string.

Example:

SELECT POSITION("e" IN "Simplilearn");  

Output: 

8

• TRIM: Removes blank space from a given string.

Example:

SELECT TRIM("  Simplilearn  ");  

Output: 

Simplilearn

• UPPER: Converts the string to uppercase.

Example:

SELECT UPPER("Simplilearn");  

Output: 

SIMPLILEARN

• LOWER: Converts the string to lowercase.

Example:

SELECT LOWER("SIMPLILEARN");  

Output: 

simplilearn

5. Why does Multiload support Non-Unique Secondary Index (NUSI) but not Unique Secondary Index (USI)?

Teradata allows the independent operation of all AMPs. With USI, the index subtable would be required to be present on multiple AMPs. This situation would need communication between AMPs. With NUSI, the index subtable is present on the same AMP as the data row, allowing that AMP to be handled independently. As a result, NUSI is supported by multi-load but not USI. 

Teradata Interview Questions for Practice

1. What is performance tuning, and why is it important?
2. How would you restart the MLOAD Client System after its failure?
3. State the process of restarting MLOAD Teradata Server after execution
4. What do you understand about skewness in Teradata?
5. What is Spool space? Explain its usage.
6. What are nodes in Teradata?
7. What ETL (Extract, Transform, and Load) tools come under Teradata?
8. State the benefits of using ETL tools over Teradata. 
9. What is caching in Teradata?
10. What is a channel driver?

Teradata Interview Questions for Experienced

1. What are Teradata utilities? Explain the various types of Teradata utilities.
2. How would you run Teradata jobs on a UNIX platform?
3. How is Teradata different from Oracle?
4. What measures will you opt for if the Fast Load Script doesn't run reliably?
5. What steps will you follow to check the current version of Teradata?
6. What table types does Teradata support?
7. Name the most commonly used BTEQ scripts.
8. What do you understand about PDE (Parallel Data Extension)?
9. What is a Partitioned Primary Index or PPI?
10. What are locks? Explain the different types of locks in Teradata.
11. What is a fallback? 
12. How would you find duplicate records in a table?

Teradata SQL Interview Questions For Freshers

1. What do you understand about FAST EXPORT in Teradata?
2. How many populated tables does Teradata MultiLoad support? 
3. Explain transient journaling and database privileges in Teradata.
4. What privilege levels does Teradata contain?
5. What is the difference between the GIVE and the GRANT statement in Teradata?
6. Explain the different GRANT forms in Teradata. 
7. How would you use GRANT (SQL Form) and GRANT (MONITOR Form)?
8. What is the use of the REVOKE statement in Teradata?

Teradata SQL Interview Questions For Experienced

1. What is the role of the SHOW statement?
2. What is HSN or Hot Standby Nodes in Teradata?
3. Explain volatile tables in Teradata.
4. Explain the difference between LOG and NO LOG in Teradata.
5. What is permanent journaling?
6. What is MERGEBLOCKRATIO in Teradata?
7. What do you understand about DATABLOCKSIZE in Teradata?
8. What BLOCK COMPRESSION?
9. What are surrogate keys in Teradata?
10. How are PRIMARY KEY Constraints different from UNIQUE Constraints in Teradata?

Teradata Developer Interview Questions 

1. What is Columnar in Teradata? Write its sample code.
2. What data protection features does Teradata offer?
3. What do you understand about RAID in Teradata?
4. What are cliques? 
5. What are the different set operators in Teradata?
6. What is the role of CASE Expression?
7. State the significance of the UPSERT command in Teradata?

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Conclusion

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