CRUD with Eloquent in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does CRUD stand for in the context of Eloquent?

CRUD stands for Create, Read, Update, and Delete. These are the four basic operations you can perform on database records using Eloquent.

beginner

How do you create a new record using Eloquent?

You create a new record by creating a new model instance, setting its properties, and then calling the save() method. For example:
$user = new User();
$user->name = 'Alice';
$user->save();

beginner

How do you retrieve all records from a table using Eloquent?

Use the all() method on the model to get all records. For example:
$users = User::all();
This returns a collection of all user records.

beginner

How do you update an existing record with Eloquent?

First, find the record by its ID, then change the properties, and call save(). For example:
$user = User::find(1);
$user->name = 'Bob';
$user->save();

beginner

How do you delete a record using Eloquent?

Find the record and call the delete() method. For example:
$user = User::find(1);
$user->delete();
This removes the record from the database.

Which Eloquent method retrieves all records from a table?

A first()

B get()

C find()

D all()

The all() method returns all records from the model's table as a collection.

What is the correct way to save a new record in Eloquent?

A $user = new User(); $user->save();

B $user = User::find(1); $user->save();

C User::all();

D User::delete();

Creating a new model instance and calling save() stores a new record.

How do you update a record with ID 5 in Eloquent?

A $user = new User(); $user->save();

B User::all();

C $user = User::find(5); $user->name = 'New'; $user->save();

D User::delete(5);

Find the record by ID, change properties, then save to update.

Which method deletes a record in Eloquent?

A delete()

B remove()

C destroy()

D erase()

The delete() method removes the record from the database.

What does the find() method do in Eloquent?

A Creates a new record

B Finds a record by its primary key

C Deletes a record

D Retrieves all records

find() looks up a record by its primary key, usually the ID.

Explain how to perform all four CRUD operations using Eloquent in Laravel.

Think about how you handle records step-by-step for each operation.

Describe the role of the save() method in Eloquent CRUD operations.

save() is key for both creating and updating.

Practice

1. Which Eloquent method is used to add a new record to the database in Laravel?

easy

A. create()

B. find()

C. delete()

D. update()

Solution

1. Step 1: Understand the purpose of create()

   The create() method in Eloquent is designed to add a new record to the database by passing an array of attributes.

2. Step 2: Compare with other methods

   find() retrieves a record, delete() removes a record, and update() modifies an existing record. None of these add new records.

3. Final Answer:

   create() -> Option A

4. Quick Check:

   Add new record = create() [OK]

Hint: Use create() to add new data fast [OK]

Common Mistakes:

• Confusing find() with create()
• Using update() to add new records
• Trying to delete() to add data

2. Which of the following is the correct syntax to find a record by its ID using Eloquent?

easy

A. $user = User->find($id);

B. $user = User::findById($id);

C. $user = User::find($id);

D. $user = User.find($id);

Solution

1. Step 1: Recall Eloquent static method syntax

   Eloquent uses static methods on the model class, so User::find($id) is correct.

2. Step 2: Identify incorrect syntax

   User->find($id) is invalid because User is a class, not an object. findById() does not exist. User.find() is not PHP syntax.

3. Final Answer:

   $user = User::find($id); -> Option C

4. Quick Check:

   Find by ID uses ::find() [OK]

Hint: Use double colon :: for static methods [OK]

Common Mistakes:

• Using arrow -> on class name
• Calling non-existent findById() method
• Using dot . notation like JavaScript

3. What will be the output of this code snippet assuming a user with ID 5 exists?

$user = User::find(5);
if ($user) {
  $user->name = 'Alice';
  $user->save();
  echo 'Updated';
} else {
  echo 'Not found';
}

medium

A. Updated

B. Not found

C. Error: save() method missing

D. No output

Solution

1. Step 1: find(5) execution

   Since a user with ID 5 exists, User::find(5) returns an Eloquent model instance, making $user truthy.

2. Step 2: Update and save

   The if ($user) condition passes, so name is set to 'Alice', save() persists it to the database, and 'Updated' is echoed.

3. Final Answer:

   Updated -> Option A

4. Quick Check:

   Record found and saved = 'Updated' [OK]

Hint: If find() returns object, save() updates record [OK]

Common Mistakes:

• Assuming save() is missing
• Thinking find() throws error if no record
• Expecting no output when record exists

4. Identify the error in this code that tries to delete a user by ID:

$user = User::find($id);
$user->delete($id);

medium

A. delete() method does not exist in Eloquent

B. find() should be replaced with findOrFail()

C. You must call save() after delete()

D. delete() should be called without arguments

Solution

1. Step 1: Understand delete() method usage

   In Eloquent, delete() is called on the model instance without any arguments to remove that record.

2. Step 2: Identify the incorrect argument

   The code incorrectly passes $id to delete(), which expects no parameters. This causes an error.

3. Final Answer:

   delete() should be called without arguments -> Option D

4. Quick Check:

   delete() takes no parameters [OK]

Hint: Call delete() directly on model instance without args [OK]

Common Mistakes:

• Passing ID to delete() method
• Thinking delete() needs save() after
• Confusing delete() with static method

5. You want to update a user's email only if the user exists and the new email is not empty. Which code snippet correctly does this using Eloquent?

hard

A. $user = User::find($id);if ($newEmail) { $user->email = $newEmail; $user->save();}

B. $user = User::find($id);if ($user && !empty($newEmail)) { $user->email = $newEmail; $user->save();}

C. $user = User::findOrFail($id);$user->email = $newEmail;$user->save();

D. $user = User::where('id', $id)->update(['email' => $newEmail]);

Solution

1. Step 1: Check user existence and email validity

   $user = User::find($id);
   if ($user && !empty($newEmail)) {
     $user->email = $newEmail;
     $user->save();
   }

   checks if $user exists and $newEmail is not empty before updating, preventing errors or empty updates.

2. Step 2: Compare other options

   $user = User::find($id);
   if ($newEmail) {
     $user->email = $newEmail;
     $user->save();
   }

   skips user existence check, risking errors if user is null.

   $user = User::findOrFail($id);
   $user->email = $newEmail;
   $user->save();

   uses findOrFail() which throws exception if user missing, no email empty check.

   $user = User::where('id', $id)->update(['email' => $newEmail]);

   updates directly but does not check if $newEmail is empty.

3. Final Answer:

   $user = User::find($id);
   if ($user && !empty($newEmail)) {
     $user->email = $newEmail;
     $user->save();
   }

   -> Option B

4. Quick Check:

   Check user and email before save [OK]

Hint: Always check user exists and data valid before save [OK]

Common Mistakes:

• Not checking if user exists before update
• Skipping validation of new email
• Using findOrFail without handling exceptions