You have a junction table MemberGroup with columns MemberID and GroupID. A query:

medium📝 Debug Q7 of 15

SQL - Table Relationships

You have a junction table MemberGroup with columns MemberID and GroupID. A query:

SELECT * FROM MemberGroup WHERE MemberID = 7 AND GroupID = 15;

returns no rows, but you know member 7 belongs to group 15. What could be a reason?

AThe values in the query do not match the actual data types or casing

BThe junction table does not support many-to-many relationships

CThe query syntax is invalid

DMemberID and GroupID are not foreign keys

Step-by-Step Solution

Solution:

Step 1: Understand the problem
The query returns no rows despite known membership.
Step 2: Possible causes
Data type mismatch or case sensitivity can cause no matches.
Step 3: Eliminate other options
Junction tables support many-to-many; syntax is valid; foreign keys not mandatory for query.
Final Answer:
The values in the query do not match the actual data types or casing -> Option A
Quick Check:
Check data types and case sensitivity [OK]

Quick Trick: Check data types and case sensitivity [OK]

Common Mistakes:

MISTAKES

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