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What is the main purpose of using multiple LEFT JOIN clauses in a single SQL query?

easy📝 Conceptual Q11 of 15
SQL - LEFT and RIGHT JOIN
What is the main purpose of using multiple LEFT JOIN clauses in a single SQL query?
ATo delete rows from multiple tables at once
BTo combine rows from several tables while keeping all rows from the first table
CTo return only rows that have matching values in all joined tables
DTo update multiple tables simultaneously
Step-by-Step Solution
Solution:
  1. Step 1: Understand LEFT JOIN behavior

    A LEFT JOIN returns all rows from the left (first) table and matching rows from the right table. If no match, NULLs appear.
  2. Step 2: Apply to multiple LEFT JOINs

    Using multiple LEFT JOINs keeps all rows from the main table and adds data from each joined table if available.
  3. Final Answer:

    To combine rows from several tables while keeping all rows from the first table -> Option B
  4. Quick Check:

    Multiple LEFT JOINs keep all main table rows [OK]
Quick Trick: LEFT JOIN keeps all main table rows even if others miss data [OK]
Common Mistakes:
MISTAKES
  • Confusing LEFT JOIN with INNER JOIN which filters rows
  • Thinking LEFT JOIN deletes or updates data
  • Assuming NULLs mean errors instead of missing matches

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