CRUD with Prisma in NestJS - Step-by-Step Execution

Concept Flow - CRUD with Prisma

Start CRUD Operation

↓

Receive Request

↓

Call Prisma Client Method

↓

Database Executes Query

↓

Return Result to Controller

↓

Send Response to Client

↓

End

This flow shows how a CRUD operation with Prisma in NestJS starts from a request, calls Prisma methods to interact with the database, and returns the result back to the client.

Execution Sample

NestJS

async createUser(data) {
  return await this.prisma.user.create({ data });
}

This code creates a new user record in the database using Prisma's create method.

Execution Table

Step	Action	Prisma Method Called	Input Data	Database Result	Response Sent
1	Receive create user request	N/A	{ name: 'Alice', email: '[e-mail]' }	N/A	N/A
2	Call prisma.user.create	create	{ name: 'Alice', email: '[e-mail]' }	User record created with id 1	N/A
3	Database executes insert query	N/A	N/A	Inserted user with id 1	N/A
4	Return created user object	N/A	N/A	{ id: 1, name: 'Alice', email: '[e-mail]' }	N/A
5	Send response to client	N/A	N/A	N/A	{ id: 1, name: 'Alice', email: '[e-mail]' }

💡 Request completed after sending created user data as response

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
data	undefined	{ name: 'Alice', email: '[e-mail]' }	{ name: 'Alice', email: '[e-mail]' }	{ name: 'Alice', email: '[e-mail]' }	N/A
result	undefined	undefined	{ id: 1, name: 'Alice', email: '[e-mail]' }	{ id: 1, name: 'Alice', email: '[e-mail]' }	{ id: 1, name: 'Alice', email: '[e-mail]' }

Key Moments - 3 Insights

Why do we await the prisma.user.create call?

Because prisma.user.create returns a promise that resolves when the database operation finishes. Awaiting it ensures we get the created user data before continuing, as shown in execution_table step 2.

What happens if the input data is missing required fields?

Prisma will throw an error during the database query (step 3), and the request will fail before sending a response (step 5). This is why validation before calling Prisma is important.

Is the database query synchronous or asynchronous?

It is asynchronous. The code waits for the database to finish (step 3) before returning the result (step 4), which is why async/await is used.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'result' after step 2?

A undefined

B User record created with id 1

C N/A

D Inserted user with id 1

💡 Hint

Check the 'Response Sent' column at step 2 in the execution_table.

At which step does the database actually insert the new user?

A Step 1

B Step 3

C Step 4

D Step 5

💡 Hint

Look for the step mentioning 'Database executes insert query' in the execution_table.

If the input data was missing the email, what would likely happen?

A Prisma would throw an error during the database query

B The request would succeed but return empty data

C The user would be created with a null email

D The response would be sent before database insertion

💡 Hint

Refer to the key_moments about missing required fields and errors.

Concept Snapshot

CRUD with Prisma in NestJS:
- Use async methods like prisma.model.create(data)
- Await promises to get results
- Input data must match schema
- Prisma sends queries to DB asynchronously
- Return DB results to client
- Handle errors for missing or invalid data

Full Transcript

This visual execution trace shows how a create operation works with Prisma in a NestJS app. First, the app receives a request with user data. Then it calls prisma.user.create with that data and awaits the result. The database inserts the new user record asynchronously. Once done, Prisma returns the created user object. Finally, the app sends this user data back to the client as a response. Variables like input data and result change step-by-step. Key points include awaiting Prisma calls to handle async DB operations and validating input to avoid errors. The quiz questions help check understanding of these steps.

Practice

1. In NestJS with Prisma, which method is used to retrieve multiple records from the database?

easy

A. create

B. update

C. findMany

D. delete

Solution

1. Step 1: Understand Prisma CRUD methods

   Prisma provides create to add, findMany to get multiple records, update to change, and delete to remove records.

2. Step 2: Identify method for retrieving multiple records

   The method findMany is specifically designed to fetch many records from the database.

3. Final Answer:

   findMany -> Option C

4. Quick Check:

   Retrieve multiple records = findMany [OK]

Hint: Remember: findMany fetches many records [OK]

Common Mistakes:

• Confusing create with findMany
• Using update to retrieve data
• Trying to delete to get records

2. Which of the following is the correct syntax to create a new user record using Prisma in a NestJS service?

easy

A. this.prisma.user.create({ data: { name: 'Alice' } })

B. this.prisma.user.findMany({ data: { name: 'Alice' } })

C. this.prisma.user.update({ data: { name: 'Alice' } })

D. this.prisma.user.delete({ data: { name: 'Alice' } })

Solution

1. Step 1: Identify the method to add a record

   The create method is used to add new records in Prisma.

2. Step 2: Check the syntax for creating a user

   The correct syntax is this.prisma.user.create({ data: { ... } }) where data holds the new record's fields.

3. Final Answer:

   this.prisma.user.create({ data: { name: 'Alice' } }) -> Option A

4. Quick Check:

   Create new record = create method [OK]

Hint: Use create with data object to add records [OK]

Common Mistakes:

• Using findMany instead of create
• Passing data to update without where clause
• Using delete method to add records

3. Given this Prisma update call in a NestJS service:

this.prisma.user.update({ where: { id: 5 }, data: { email: '[e-mail]' } })

What will this operation do?

medium

A. Delete the user with id 5

B. Update the email of the user with id 5 to '[e-mail]'

C. Create a new user with id 5 and email '[e-mail]'

D. Return all users with email '[e-mail]'

Solution

1. Step 1: Understand the update method parameters

   The update method requires a where clause to find the record and data to specify changes.

2. Step 2: Analyze the given call

   It targets user with id: 5 and changes the email field to '[e-mail]'.

3. Final Answer:

   Update the email of the user with id 5 to '[e-mail]' -> Option B

4. Quick Check:

   Update with where and data changes record [OK]

Hint: Update needs where to find record, data to change [OK]

Common Mistakes:

• Thinking update creates new records
• Confusing update with delete
• Missing where clause causes errors

4. What is wrong with this Prisma delete call in a NestJS service?

this.prisma.user.delete({ data: { id: 3 } })

medium

A. The delete method should use a where clause, not data

B. The delete method cannot delete by id

C. The syntax is correct and will delete user with id 3

D. The delete method requires an update object

Solution

1. Step 1: Check Prisma delete method syntax

   The delete method requires a where clause to specify which record to remove.

2. Step 2: Identify the error in the code

   The code incorrectly uses data instead of where, causing a syntax error.

3. Final Answer:

   The delete method should use a where clause, not data -> Option A

4. Quick Check:

   Delete needs where, not data [OK]

Hint: Delete uses where to find record, not data [OK]

Common Mistakes:

• Using data instead of where in delete
• Trying to update in delete method
• Omitting where clause causes errors

5. You want to update a user's name only if the user exists, otherwise create a new user with that name using Prisma in NestJS. Which approach correctly handles this logic?

hard

A. Use delete then create to replace the user

B. Call update and if it fails, call create manually

C. Use findMany then create without update

D. Use upsert with where, update, and create objects

Solution

1. Step 1: Understand Prisma's upsert method

   The upsert method updates a record if it exists or creates it if not, combining both actions safely.

2. Step 2: Identify correct usage for conditional update or create

   Using upsert with where to find the user, update for changes, and create for new record is the best practice.

3. Final Answer:

   Use upsert with where, update, and create objects -> Option D

4. Quick Check:

   Conditional update or create = upsert [OK]

Hint: Use upsert to update or create in one call [OK]

Common Mistakes:

• Manually catching update errors to create
• Using findMany without update
• Deleting before creating wastes operations