SQL - Table Constraints
Which of the following is the correct syntax to add a foreign key with ON UPDATE SET NULL in SQL?
Which of the following is the correct syntax to add a foreign key with ON UPDATE SET NULL in SQL?
easy📝 Syntax Q12 of 15
Step-by-Step Solution
Solution:
Step 1: Identify correct ON UPDATE syntax
The syntax for foreign key with ON UPDATE SET NULL is: FOREIGN KEY (...) REFERENCES ... ON UPDATE SET NULL.Step 2: Check options for ON UPDATE SET NULL
FOREIGN KEY (child_id) REFERENCES parent(id) ON UPDATE SET NULL matches the correct syntax exactly. Others either use ON DELETE or different actions.Final Answer:
FOREIGN KEY (child_id) REFERENCES parent(id) ON UPDATE SET NULL -> Option AQuick Check:
ON UPDATE SET NULL syntax = FOREIGN KEY (child_id) REFERENCES parent(id) ON UPDATE SET NULL [OK]
Quick Trick: ON UPDATE SET NULL sets child keys to NULL on parent update [OK]
Common Mistakes:
MISTAKES- Using ON DELETE instead of ON UPDATE
- Mixing CASCADE and SET NULL in syntax
- Omitting REFERENCES keyword
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