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Demonstrate how to use a LEFT JOIN to combine data from two tables and handle null values.

SQLmedium0.4 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
Wipro
Key Concepts Tested
join
Expert AnswerPremium
83 wordsInterview-ready
**Architectural Logic**: LEFT JOIN preserves left rows; nulls arise from non-matches—handle for display and aggregation. **Example**: `SELECT o.order_id, c.customer_name, COALESCE(c.city, 'Unknown') AS city FROM orders o LEFT JOIN customers c ON o.customer_id = c.id`. **Aggregation**: `COUNT(c.id)` counts matches; `COUNT(*)` counts all left. Use COALESCE/IFNULL for display; CASE for conditional logic....
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