SQL - Table Relationships
You want to create a foreign key from Orders to Customers but allow Orders without a customer (optional link). Which is the best approach?
You want to create a foreign key from Orders to Customers but allow Orders without a customer (optional link). Which is the best approach?
hard📝 Application Q9 of 15
Step-by-Step Solution
Solution:
Step 1: Understand optional foreign key relationships
To allow missing links, the foreign key column must accept NULL values.Step 2: Choose correct constraint setup
Making the column nullable and adding the foreign key constraint enforces links when present but allows NULLs.Final Answer:
Make the foreign key column nullable and add the foreign key constraint. -> Option DQuick Check:
Nullable foreign key allows optional links [OK]
Quick Trick: Nullable foreign key column allows optional references [OK]
Common Mistakes:
MISTAKES- Making foreign key NOT NULL blocks optional links
- Skipping foreign key constraint loses referential integrity
- Confusing primary key with foreign key
Master "Table Relationships" in SQL
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