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/General/Other/APPLY Operator - CROSS APPLY and OUTER APPLY

APPLY Operator - CROSS APPLY and OUTER APPLY

General/Othermedium0.3 min readPremium

Frequency

Low

Asked at 1 company

Category

243

questions in General/Other

Difficulty Split

151E|43M|49H

in this category

Total Bank

1,863

across 7 categories

Asked at these companies

Interview Pro Tip

Pro-Move: 'We use CROSS APPLY for JSON parsing in SQL Server—moved from 10 UDF calls to single APPLY; 3× faster.' Red Flag: Using APPLY for set-based operations—often a JOIN is better.

Key Concepts Tested

Expert AnswerPremium

64 wordsInterview-ready

**CROSS APPLY**: Invokes table-valued function/subquery per row; like INNER JOIN—excludes rows where function returns nothing. **OUTER APPLY**: Like LEFT JOIN—keeps all left rows, NULL where function returns nothing. **Use**: Correlated subqueries, JSON parsing, string splitting. **PostgreSQL**: LATERAL JOIN (CROSS JOIN LATERAL, LEFT JOIN LATERAL). **Performance**: Can be expensive—row-by-row. Prefer set-based 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 Kaseya. 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

Related General/Other Questions

hardHave you worked on Data Warehousing projects?Free mediumHow would you read data from a web API? What steps would you follow after reading the data?Free hardRetrieve the most recent sale_timestamp for each product (Latest Transaction).Free hardWhat is the difference between OLTP and OLAP?Free mediumWhat is the difference between SQL and NoSQL databases?Free

According to DataEngPrep.tech, this is one of the most frequently asked General/Other 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 General/Other questions →