Apache Hive Interview Questions and Answers

Ques 1. What is Apache Hive?

Apache Hive is a data warehousing and SQL-like query language for Apache Hadoop.

Example:

SELECT * FROM table_name;

Ques 2. What is HiveQL?

Hive Query Language (HiveQL) is a SQL-like language used to query data stored in Hive.

Example:

SELECT column1, column2 FROM table_name WHERE condition;

Ques 3. What is the purpose of Hive metastore?

Hive metastore stores metadata about Hive tables, partitions, and databases.

Ques 4. What is the purpose of Hive SerDe?

Hive SerDe (Serializer/Deserializer) is used to read and write data in custom formats.

Ques 5. What is the purpose of Hive partitions?

Hive partitions allow you to divide a table into smaller, more manageable parts based on a specific column.

Ques 6. What is the purpose of Hive HCatalog?

HCatalog is a storage and table management layer for Hadoop that enables sharing of data between Pig, MapReduce, and Hive.

Ques 7. What is Hive's role in the Hadoop ecosystem?

Hive provides a high-level SQL-like interface for querying and analyzing data stored in Hadoop Distributed File System (HDFS).

Ques 8. What are the types of Hive tables?

Hive supports managed tables (internal) and external tables. Managed tables store data in a Hive-controlled location, while external tables reference data stored outside Hive.

Ques 9. How can you limit the number of rows returned in a Hive query?

You can use the 'LIMIT' clause to restrict the number of rows returned in a Hive query.

Example:

SELECT * FROM table_name LIMIT 10;

Ques 10. Explain the key features of Apache Hive.

Key features include SQL-like queries (HiveQL), schema-on-read, extensibility, and scalability.

Ques 11. Differentiate between Hive and HBase.

Hive is a data warehousing solution, whereas HBase is a NoSQL database for real-time read/write access to large datasets.

Ques 12. Explain the difference between Hive and traditional relational databases.

Hive is schema-on-read, while traditional databases are schema-on-write.

Ques 13. How can you load data into Hive from an external table?

You can use the 'LOAD DATA INPATH' or 'INSERT OVERWRITE' command to load data into Hive from an external table.

Example:

LOAD DATA INPATH '/path/to/data' INTO TABLE table_name;

Ques 14. What is the purpose of Hive UDFs (User-Defined Functions)?

Hive UDFs allow users to define custom functions to perform operations not supported by built-in functions.

Ques 15. Explain Hive's internal architecture.

Hive consists of a query compiler, query optimizer, execution engine, and a metastore for storing metadata.

Ques 16. How can you perform data sorting in Hive?

You can use the 'SORT BY' clause in the 'CREATE TABLE' statement to achieve data sorting in Hive.

Example:

CREATE TABLE sorted_table (column1 INT, column2 STRING) SORT BY column1;

Ques 17. What are the differences between Hive and Pig?

Hive is SQL-based, while Pig uses a scripting language called Pig Latin. Hive is suitable for data warehousing, while Pig is more versatile for data processing.

Ques 18. How can you join tables in Hive?

You can perform joins in Hive using the standard SQL syntax, such as INNER JOIN, LEFT JOIN, and RIGHT JOIN.

Example:

SELECT * FROM table1 t1 INNER JOIN table2 t2 ON t1.id = t2.id;

Ques 19. How can you handle null values in Hive?

You can use the 'COALESCE' function or 'CASE' statement to handle null values in Hive queries.

Example:

SELECT column1, COALESCE(column2, 'NA') FROM table_name;

Ques 20. Explain dynamic partitioning in Hive.

Dynamic partitioning in Hive allows the automatic creation of partitions based on a specified column during the data insertion process.

Ques 21. How does Hive handle schema evolution?

Hive supports schema evolution, allowing the addition of new columns to existing tables without affecting the older data.

Ques 22. How can you enable Hive vectorization?

You can enable Hive vectorization by setting the 'hive.vectorized.execution.enabled' configuration property to true.

Ques 23. How can you perform data sampling in Hive?

You can use the 'TABLESAMPLE' clause in the 'SELECT' statement to perform data sampling in Hive.

Example:

SELECT * FROM table_name TABLESAMPLE(BUCKET x OUT OF total);

Ques 24. Explain the use of Hive's EXPLAIN statement.

The 'EXPLAIN' statement in Hive provides the execution plan of a query, helping in query optimization and troubleshooting.

Example:

EXPLAIN SELECT * FROM table_name;

Ques 25. How can you optimize Hive queries for better performance?

Optimizations include partitioning, bucketing, using indexes, and tuning query execution parameters.

Ques 26. What is Hive bucketing, and how is it useful?

Hive bucketing is a technique to divide data into buckets based on a hash function, improving query performance. It helps avoid full table scans.

Ques 27. What is the purpose of Hive indexes?

Hive indexes provide a way to speed up query processing by allowing faster access to rows that meet certain conditions.

Ques 28. What is Hive's ACID support, and when is it used?

Hive ACID (Atomicity, Consistency, Isolation, Durability) support is used for managing transactions in Hive tables.

Ques 29. What is the purpose of Hive skew join optimization?

Hive skew join optimization is used to handle skewed data distribution during join operations, improving performance.

Ques 30. What is the purpose of Hive's distributed cache?

Hive's distributed cache is used to distribute small read-only files, such as lookup tables, to all the nodes in a Hadoop cluster for improved performance.