You have a parent table and two child tables referencing it. Child table A uses ON DELETE CASCADE, child table B uses ON DELETE SET NULL. If a parent row is deleted, what happens?

hard📝 Application Q8 of 15

SQL - Table Constraints

You have a parent table and two child tables referencing it. Child table A uses ON DELETE CASCADE, child table B uses ON DELETE SET NULL. If a parent row is deleted, what happens?

ABoth child tables delete their rows.

BChild table A rows are deleted; child table B rows have foreign keys set to NULL.

CBoth child tables set foreign keys to NULL.

DParent delete is blocked if any child rows exist.

Step-by-Step Solution

Solution:

Step 1: Understand each ON DELETE action
CASCADE deletes child rows; SET NULL sets foreign keys to NULL.
Step 2: Apply to each child table
Child table A rows referencing the parent are deleted; child table B rows have foreign keys set to NULL.
Final Answer:
Child table A rows deleted; child table B foreign keys set to NULL. -> Option B
Quick Check:
CASCADE deletes, SET NULL clears foreign keys [OK]

Quick Trick: CASCADE deletes; SET NULL clears foreign keys [OK]

Common Mistakes:

MISTAKES

Assuming both child tables behave the same
Thinking parent delete is blocked
Confusing SET NULL with delete

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More SQL Quizzes

You have a parent table and two child tables referencing it. Child table A uses ON DELETE CASCADE, child table B uses ON DELETE SET NULL. If a parent row is deleted, what happens?

Step 1: Understand each ON DELETE action

Step 2: Apply to each child table

Final Answer:

Quick Check:

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