Solution:Step 1: Understand ON DELETE RESTRICT effectRESTRICT prevents deleting a parent row if any child rows reference it.Step 2: Apply to given dataSince child row with parent_id=1 exists, deleting parent id=1 is blocked.Final Answer:The delete fails because the child row exists and ON DELETE RES

[Solved] Given these tables:CREATE TABLE parent (id INT PRIMARY KEY);CREATE TABLE child (id INT PRIMARY KEY, parent_id INT, FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE RESTRICT);INSERT INTO parent... | SQL

SQL - Table Constraints

Given these tables:

CREATE TABLE parent (id INT PRIMARY KEY);
CREATE TABLE child (id INT PRIMARY KEY, parent_id INT, FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE RESTRICT);
INSERT INTO parent VALUES (1);
INSERT INTO child VALUES (10, 1);

What happens if you run DELETE FROM parent WHERE id = 1;?

AThe parent row is deleted, and the child row is also deleted.

BThe parent row is deleted, but the child row's parent_id is set to NULL.

CThe delete succeeds and leaves the child row with a dangling parent_id.

DThe delete fails because the child row exists and ON DELETE RESTRICT blocks it.

Step-by-Step Solution

Solution:

Step 1: Understand ON DELETE RESTRICT effect
RESTRICT prevents deleting a parent row if any child rows reference it.
Step 2: Apply to given data
Since child row with parent_id=1 exists, deleting parent id=1 is blocked.
Final Answer:
The delete fails because the child row exists and ON DELETE RESTRICT blocks it. -> Option D
Quick Check:
ON DELETE RESTRICT blocks delete if children exist [OK]

Quick Trick: RESTRICT blocks delete if child rows exist [OK]

Common Mistakes:

MISTAKES

Assuming CASCADE behavior with RESTRICT
Thinking child foreign key becomes NULL
Believing delete always succeeds

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More SQL Quizzes

Given these tables:

Step 1: Understand ON DELETE RESTRICT effect

Step 2: Apply to given data

Final Answer:

Quick Check:

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