SQL - LEFT and RIGHT JOIN
Why might you use multiple
LEFT JOIN clauses instead of multiple INNER JOIN clauses?Why might you use multiple LEFT JOIN clauses instead of multiple INNER JOIN clauses?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Compare LEFT JOIN and INNER JOIN
INNER JOIN returns only rows with matches in all tables, while LEFT JOIN keeps all rows from the left table.Step 2: Reason for multiple LEFT JOINs
Using multiple LEFT JOINs ensures all rows from the main table appear, even if some joined tables lack matching rows.Final Answer:
To include all rows from the main table even if related tables have no matching rows. -> Option BQuick Check:
LEFT JOIN preserves left rows = To include all rows from the main table even if related tables have no matching rows. [OK]
Quick Trick: LEFT JOIN keeps main table rows even without matches [OK]
Common Mistakes:
MISTAKES- Confusing LEFT JOIN with INNER JOIN
- Assuming unmatched rows are excluded
- Believing LEFT JOIN speeds up queries
Master "LEFT and RIGHT JOIN" in SQL
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