DataEngPrep.tech
QuestionsBlogStore
Get PDF Bundle
Home/Questions/SQL/What are some best practices for writing efficient SQL queries?

What are some best practices for writing efficient SQL queries?

SQLmedium0.6 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Freecharge
Key Concepts Tested
joinpartitionsql
Expert AnswerPremium
124 wordsInterview-ready
Efficient SQL best practices: (1) Select only needed columns—avoid SELECT *. (2) Use WHERE to filter early—before JOINs when possible. (3) Leverage indexes/partitioning—filter on partitioned columns. (4) Avoid functions on indexed columns—e.g., WHERE YEAR(date) = 2024 prevents index use; use date ranges. (5) Use EXISTS instead of IN for subqueries when checking existence. (6) Prefer JOIN over subqueries for clarity and optimizer support. (7) Use appropriate join types—INNER when possible....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like Freecharge. The answer also includes follow-up discussion points that interviewers commonly explore.

Continue Reading the Full Answer

Unlock the complete expert answer with code examples, trade-offs, and pro tips - plus 1,863+ more.

Create Free Account - Unlock 30 Answers
Get PDF Bundle - from $21

Or upgrade to Platform Pro - $39

Engineers who used these answers got offers at

AmazonDatabricksSnowflakeGoogleMeta

Free: Top 20 SQL Interview Questions (PDF)

Get the most asked SQL questions with expert answers. Instant download.

No spam. Unsubscribe anytime.

Related SQL Questions

mediumWrite an SQL query to find the second-highest salary from an employee table.FreemediumDemonstrate the difference between DENSE_RANK() and RANK()FreemediumDiscuss differences between ROW_NUMBER(), RANK(), and DENSE_RANK(), and provide examples from your projects.FreemediumExplain the differences between Data Warehouse, Data Lake, and Delta LakeFreemediumExplain the differences between Repartition and Coalesce. When would you use each?Free

According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

← Back to all questionsMore SQL questions →