DataEngPrep.tech

JavaScript is required to use this application. Please enable JavaScript in your browser settings or disable any extensions that may be blocking scripts.

DataEngPrep.tech

Questions Blog Store

Home/Questions/SQL/SQL Question - Inner Join with Null Handling, compute total row count

SQL Question - Inner Join with Null Handling, compute total row count

SQLmedium0.5 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

Key Concepts Tested

Expert AnswerPremium

91 wordsInterview-ready

INNER JOIN with NULL: NULL keys don't match (NULL = NULL is false), so they're excluded. Count: SELECT COUNT(*) FROM a INNER JOIN b ON a.key = b.key. If key has nulls, inner join count is less than min(|a|,|b|). To include null matches: ON (a.key = b.key OR (a.key IS NULL AND b.key IS NULL)). Count depends on null handling. **Why it matters**: Design choices compound at scale—wrong approach can cause 100× overhead....

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 Paytm. 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.Free mediumDemonstrate the difference between DENSE_RANK() and RANK()Free mediumDiscuss differences between ROW_NUMBER(), RANK(), and DENSE_RANK(), and provide examples from your projects.Free mediumExplain the differences between Data Warehouse, Data Lake, and Delta LakeFree mediumExplain 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 questions More SQL questions →