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Foreign Key Constraint Violation in Laravel - Fix
This error occurs when trying to insert a foreign key value that doesn't exist in the parent table.
The Error
Error Message
SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child rowCommon Causes
- 1 Referenced parent record doesn't exist
- 2 Wrong foreign key value provided
- 3 Parent record deleted before child insertion
- 4 Migration order issues creating tables
Solutions
1
Ensure parent record exists first
PHP
$user = User::findOrFail($userId);
Post::create([
'title' => 'My Post',
'user_id' => $user->id,
]);
2
Add validation for foreign key
PHP
$request->validate([
'user_id' => 'required|exists:users,id',
'category_id' => 'required|exists:categories,id',
]);
3
Use cascade on delete in migration
PHP
$table->foreignId('user_id')
->constrained()
->onDelete('cascade');
4
Set null on delete for optional relationships
PHP
$table->foreignId('category_id')
->nullable()
->constrained()
->nullOnDelete();Need Help With Your Laravel Project?
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About Hafiz
Full Stack Developer from Italy. I build web applications with Laravel and Vue.js, and automate business processes. Creator of ReplyGenius, StudyLab, and other SaaS products.
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