TCS Snowflake Developer Interview Questions and Answers

Optimizing SQL queries involves using indexes, minimizing data retrieval, and avoiding unnecessary joins.

• Use indexes on columns frequently used in WHERE clauses

• Minimize data retrieval by selecting only necessary columns

• Avoid unnecessary joins by using subqueries or temporary tables

Time travel is a theoretical concept that involves moving between different points in time.

• Time travel is a popular theme in science fiction literature and movies.

• The concept of time travel raises questions about causality and the nature of time.

• Some theories suggest that time travel could be possible through wormholes or time machines.

The cache will be invalidated and refreshed when the query changes.

• When the query changes, the cache will be invalidated to ensure accurate results.

• The system will refresh the cache with the updated query results.

• This helps prevent outdated or incorrect data from being served from the cache.

I would rate myself 8 out of 10 in SQL. I have strong knowledge and experience in writing complex queries and optimizing database performance.

• Strong understanding of SQL syntax and commands

• Experience in writing complex queries involving multiple tables and joins

• Knowledge of database optimization techniques

• Familiarity with Snowflake specific SQL functions and features

SQL scenario: Retrieve the top 5 customers by total sales from a sales table.

• Use the SUM() function to calculate total sales for each customer.

• Group results by customer ID or name using GROUP BY.

• Order the results in descending order using ORDER BY.

• Limit the results to the top 5 using the LIMIT clause.

• Example SQL query: SELECT customer_id, SUM(sales) AS total_sales FROM sales_table GROUP BY customer_id ORDER BY total_sa...read more

Cache is a hardware or software component that stores data to reduce future data retrieval time.

• Cache is used to store frequently accessed data for quick retrieval.

• Types of cache include CPU cache, web cache, and browser cache.

• Cache helps improve performance by reducing the need to access data from slower storage mediums.

• Examples of cache include L1, L2, and L3 caches in CPUs, and caching mechanisms in web browsers.

• Cac...read more

Snowflake is a cloud-based data warehousing platform that offers features like data sharing, scalability, and performance.

• Snowflake allows for easy data sharing between organizations and departments.

• It offers scalability by allowing users to easily resize their computing resources based on their needs.

• Snowflake provides high performance through its unique architecture that separates storage and compute.

• It supports vari...read more

Types of caches include memory cache, disk cache, and browser cache.

• Memory cache stores data in memory for quick access.

• Disk cache stores data on disk for faster retrieval than from the original source.

• Browser cache stores web page elements locally to reduce loading times.

• Other types include CPU cache, page cache, and object cache.

Understanding SQL joins is crucial for combining data from multiple tables effectively.

• INNER JOIN: Returns records with matching values in both tables. Example: SELECT * FROM A INNER JOIN B ON A.id = B.id;

• LEFT JOIN: Returns all records from the left table and matched records from the right table. Example: SELECT * FROM A LEFT JOIN B ON A.id = B.id;

• RIGHT JOIN: Returns all records from the right table and matched records...read more

The LAG function in SQL retrieves data from a previous row in a result set, useful for comparisons.

• LAG function syntax: LAG(value, offset, default) OVER (PARTITION BY column ORDER BY column).

• Example: LAG(sales, 1) OVER (ORDER BY date) gives the sales from the previous day.

• Useful for calculating differences, trends, or changes over time.

• Can be combined with other window functions for advanced analytics.