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Identify the error in this SQL join:

medium📝 Debug Q6 of 15
SQL - INNER JOIN
Identify the error in this SQL join:
SELECT Orders.OrderID, Customers.Name FROM Orders JOIN Customers ON Orders.OrderID = Customers.CustomerID;
ASelecting columns not in tables
BMissing WHERE clause
CUsing JOIN instead of LEFT JOIN
DJoin condition uses wrong columns; should join on CustomerID
Step-by-Step Solution
Solution:

  1. Step 1: Check join condition columns

    Orders.OrderID is not related to Customers.CustomerID; join should be on Orders.CustomerID = Customers.CustomerID.

  2. Step 2: Understand impact of wrong join

    Wrong join condition causes incorrect or empty results.

  3. Final Answer:

    Join condition uses wrong columns; should join on CustomerID -> Option D

  4. Quick Check:

    Join keys must match related columns [OK]
Quick Trick: Join keys must be related columns [OK]
Common Mistakes:
MISTAKES
  • Mixing unrelated columns in ON clause
  • Forgetting to match foreign key to primary key
  • Assuming any columns can be joined

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