What is Join and what are the different types of Joins in SQL?
This question asks for the definition and varieties of SQL join operations. It tests practical querying skills.
Why Interviewers Ask This
Joins are the most common operation in data retrieval. Interviewers ask this to ensure you can combine data from multiple tables effectively. Mastery of joins is essential for complex reporting and analysis tasks.
How to Answer This Question
Define Join as combining rows from two tables. List types: Inner, Left, Right, Full Outer, Cross. Explain the result set for each. Use simple examples to illustrate matching and non-matching rows.
Key Points to Cover
- Combining tables
- Inner vs Outer joins
- Matching logic
- Null handling
Sample Answer
A Join combines rows from two or more tables based on a related column. Inner Join returns only matching rows. Left Join includes all left rows and matches from the right. Right and Full Outer Joins cover the opposite an…
Common Mistakes to Avoid
- Confusing Left and Right
- Ignoring Cartesian products
- Not explaining NULLs in outer joins
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