Why PATCH request in Postman? - Purpose & Use Cases

The Big Idea

What if you could fix just one tiny detail without rewriting everything else?

The Scenario

Imagine you have a big form with many fields on a website. You want to update just one small detail, like your phone number. Manually changing the whole form every time is tiring and risky.

The Problem

Manually sending the entire data every time is slow and can cause mistakes. You might accidentally overwrite other information you didn't want to change. It's like rewriting a whole letter just to fix one word.

The Solution

The PATCH request lets you send only the changes you want to make. It updates just the parts you specify, keeping the rest safe. This saves time and reduces errors.

Before vs After

✗ Before

POST /user/update {"name":"John", "email":"[e-mail]", "phone":"1234567890"}

✓ After

PATCH /user/update {"phone":"1234567890"}

What It Enables

PATCH requests make updating data faster, safer, and more efficient by changing only what needs to be changed.

Real Life Example

When you update your profile picture on a social media app, the app uses PATCH to change just the picture without touching your name, bio, or other details.

Key Takeaways

Manual full updates are slow and risky.

PATCH updates only what you want to change.

This makes data updates safer and quicker.

Practice

1. What is the main purpose of a PATCH request in Postman?

easy

A. To update only specific fields of a resource without sending the entire data

B. To create a new resource on the server

C. To delete a resource completely

D. To retrieve data from the server

Solution

1. Step 1: Understand HTTP methods

   PATCH is used to update part of a resource, unlike POST (create) or DELETE (remove).

2. Step 2: Identify PATCH usage in Postman

   PATCH sends only the fields to update, not the whole resource.

3. Final Answer:

   To update only specific fields of a resource without sending the entire data -> Option A

4. Quick Check:

   PATCH updates part of resource = D [OK]

Hint: PATCH updates partial data, not full resource [OK]

Common Mistakes:

• Confusing PATCH with POST or PUT
• Thinking PATCH deletes data
• Assuming PATCH retrieves data

2. Which of the following is the correct way to set a PATCH request body in Postman to update the user's email?

easy

A. { "email": "[e-mail]" }

B. [ "email": "[e-mail]" ]

C. "email": "[e-mail]"

D. [e-mail]

Solution

1. Step 1: Recognize JSON format for PATCH body

   PATCH body must be valid JSON with key-value pairs inside curly braces.

2. Step 2: Check each option's syntax

   { "email": "[e-mail]" } uses correct JSON object syntax. Options A, C, D are invalid JSON or XML.

3. Final Answer:

   { "email": "[e-mail]" } -> Option A

4. Quick Check:

   Valid JSON object = B [OK]

Hint: Use JSON object with braces for PATCH body [OK]

Common Mistakes:

• Using square brackets instead of braces
• Omitting braces around JSON
• Using XML tags instead of JSON

3. Given this PATCH request in Postman to update a user's phone number:

{
  "phone": "[phone]"
}

If the server responds with status 200 and the updated user data including the new phone, what does this indicate?

medium

A. The request failed due to missing fields

B. The entire user data was replaced

C. The server ignored the PATCH request

D. The phone number was successfully updated partially

Solution

1. Step 1: Analyze PATCH request and response

   PATCH updates part of resource; status 200 means success; response shows updated data.

2. Step 2: Interpret server behavior

   Since only phone was sent and updated, server partially updated resource successfully.

3. Final Answer:

   The phone number was successfully updated partially -> Option D

4. Quick Check:

   PATCH success with 200 = partial update C [OK]

Hint: Status 200 + partial data = PATCH success [OK]

Common Mistakes:

• Assuming PATCH replaces entire resource
• Thinking 200 means failure
• Ignoring response content

4. You sent a PATCH request in Postman but received a 400 Bad Request error. Which of these is the most likely cause?

medium

A. The URL is correct but the method should be GET

B. The server does not support PATCH method

C. The request body is missing or malformed JSON

D. The response body is empty

Solution

1. Step 1: Understand 400 Bad Request meaning

   400 means client sent invalid request, often bad syntax or missing data.

2. Step 2: Check PATCH request common errors

   Malformed or missing JSON body is a frequent cause of 400 in PATCH requests.

3. Final Answer:

   The request body is missing or malformed JSON -> Option C

4. Quick Check:

   400 error = bad request body A [OK]

Hint: Check JSON body format if 400 error occurs [OK]

Common Mistakes:

• Confusing 400 with server errors
• Ignoring request body format
• Assuming method is unsupported without checking

5. You want to update a user's profile with a PATCH request in Postman. The user has fields: name, email, and address. You only want to update the address but accidentally send the entire user object with email set to null. What is the likely outcome?

hard

A. Only address updates; email remains unchanged

B. The address updates, but email becomes null on the server

C. The server rejects the request due to null email

D. The entire user profile is deleted

Solution

1. Step 1: Understand PATCH partial update behavior

   PATCH updates fields sent; if a field is sent as null, server may update it to null.

2. Step 2: Analyze sending entire object with null email

   Sending email as null means server likely sets email to null, not ignoring it.

3. Final Answer:

   The address updates, but email becomes null on the server -> Option B

4. Quick Check:

   PATCH sends null field = field updated to null A [OK]

Hint: PATCH null field updates it to null on server [OK]

Common Mistakes:

• Assuming null fields are ignored
• Thinking PATCH only updates non-null fields
• Expecting server to reject null values always