SQL - Table Constraints
What happens if you try to insert a record in a child table with a foreign key value that does not exist in the parent table?
What happens if you try to insert a record in a child table with a foreign key value that does not exist in the parent table?
easy📝 Conceptual Q1 of 15
Step-by-Step Solution
Solution:
Step 1: Understand foreign key enforcement
A foreign key ensures that the child table's value must exist in the parent table.Step 2: Check behavior on invalid insert
Inserting a value not present in the parent table violates the foreign key constraint, causing an error.Final Answer:
The insertion fails with a foreign key constraint error. -> Option AQuick Check:
Foreign key violation = insertion error [OK]
Quick Trick: Foreign keys prevent invalid references, causing insert errors [OK]
Common Mistakes:
MISTAKES- Assuming foreign key allows any value
- Thinking parent table auto-creates missing keys
- Believing foreign key converts invalid values to NULL
Master "Table Constraints" in SQL
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