SQL views

Prerequisites

In order to follow this guide, you need:

Limitations

Be aware of the following limitations when using views with Prisma:

• You must manually add each view as a model to the Prisma schema right now. Introspection does not add views to the schema currently.
• Views must include a unique column - such as an ID.
• The generated Prisma Client will include queries such create, delete, and update, even though you cannot perform these queries on a view.

1. Create a new database and project directory

To create a new database:

1. Create a project directory where you can put the files you'll create throughout this guide:

   $mkdir sql-views-demo
   $cd sql-views-demo

2. Next, make sure that your database server is running. Then execute the following command in your terminal to create a new database called SqlViews:

   $createdb SqlViews

   mysql -e 'CREATE DATABASE `SqlViews`;'

3. Validate that the database was created by running the following command which lists all tables (relations) in your database (right now there are none):

   $psql -d SqlViews -c "\dt"

   mysql -e 'SHOW TABLES in `SqlViews`;'

2. Create two tables with a foreign key

In this section, you'll create two tables where one references the other via a foreign key in the SqlViews database.

1. Create a new file called sql-views-tables.sql and add the following code to it:

   CREATE TABLE `SqlViews`.`User` (
     `id` INT AUTO_INCREMENT PRIMARY KEY,
     `name` VARCHAR(256),
     `email` VARCHAR(256) UNIQUE
   );
   
   CREATE TABLE `SqlViews`.`Post` (
     `id` INT AUTO_INCREMENT PRIMARY KEY,
     `title` VARCHAR(256),
     `content` VARCHAR(256),
     `published` BOOLEAN,
     `authorId` INT,
     CONSTRAINT `author` FOREIGN KEY (`authorId`) REFERENCES `User`(`id`)
   );

   CREATE TABLE "public"."User" (
     id SERIAL PRIMARY KEY,
     email TEXT UNIQUE,
     name TEXT
   );
   
   CREATE TABLE "public"."Post" (
     id SERIAL PRIMARY KEY,
     title TEXT,
     content TEXT,
     published BOOLEAN,
     "authorId" INTEGER,
     CONSTRAINT author FOREIGN KEY ("authorId") REFERENCES "public"."User" (id)
   );

2. Run the SQL statement against your database to create the two tables:

   $psql SqlViews <\ sql-views-tables.sql

   $mysql <\ sql-views-tables.sql

3. Run the following command to validate that the tables were created:

   $psql -d SqlViews -c "\dt"

   mysql -e 'SHOW TABLES in `SqlViews`;'

You just created two tables named User and Post in the database. The Post table references the User table via the foreign key defined on the authorId column.

3. Create a view named Draft

In this section you will create a view named Draft. The Draft view represents a query that returns the post title and author email of all posts that have not been published. To create a view:

1. Create a new file called sql-views-draft.sql and add the following code to it:

   CREATE VIEW "Draft" AS
       SELECT "published", "title", "email", "Post"."id"
       FROM "Post", "User"
       WHERE "published" = false AND "Post"."authorId" = "User"."id";

   CREATE VIEW Drafts AS
       SELECT published, title, email, Post.id
       FROM Post, User
       WHERE published = false AND Post.authorId = User.id;

2. Run the SQL statement against your database to create the view:

   $psql SqlViews <\ sql-views-draft.sql

   $mysql <\ sql-views-draft.sql

3. Run the following command to validate that the view was created:

   $psql -d SqlViews -c "\dv"

   mysql -e SHOW FULL TABLES in `SqlViews` WHERE TABLE_TYPE LIKE 'VIEW';'

   You should see the following list of views:

          List of relations
    Schema |  Name  | Type |  Owner
    --------+--------+------+----------
    public | Draft  | view | postgres

    +----------------+------------+
    | Tables_in_mydb | Table_type |
    +----------------+------------+
    | Drafts         | VIEW       |
    +----------------+------------+

4. Introspect your database with Prisma

In this section you'll introspect your database to generate the Prisma models for the tables that you created.

Note: You will manually add the Draft view to the Prisma schema in a later step.

1. Set up a new Node.js project and add the prisma CLI as a development dependency:

   $npm init -y
   $npm install prisma --save-dev

2. Create a new file called schema.prisma and add the following code to it:

   schema.prisma
   1datasource db {
   2  provider = "postgresql"
   3  url      = env("DATABASE_URL")
   4}

   schema.prisma
   1datasource db {
   2  provider = "mysql"
   3  url      = env("DATABASE_URL")
   4}

3. In order to introspect your database, you need to tell Prisma how to connect to it. You do so by configuring a datasource in your Prisma schema. Create a new file called .env and set your database connection URL as the DATABASE_URL environment variable:

   DATABASE_URL=postgresql://__USER__:__PASSWORD__@__HOST__:__PORT__/SqlViews

   DATABASE_URL=mysql://USER:PASSWORD@HOST:PORT/DATABASE

   In the above code snippet, you need to replace the uppercase placeholders with your own connection details. For example, if your database is running locally it could look like this:

   DATABASE_URL=postgresql://janedoe:mypassword@localhost:5432/SqlViews

   DATABASE_URL=mysql://janedoe:mypassword@localhost:3306/mydb

   The database connection URL is set via an environment variable. The Prisma CLI automatically supports the dotenv format which automatically picks up environment variables defined in a file called .env.

4. With both the schema.prisma and .env files in place, run Prisma's introspection with the following command:

   $npx prisma introspect

   This command introspects your database and for each table adds a Prisma model to the Prisma schema:

   schema.prisma
   1datasource db {
   2  provider = "postgresql"
   3  url      = env("DATABASE_URL")
   4}
   5
   6model Post {
   7  authorId  Int?
   8  content   String?
   9  id        Int     @default(autoincrement()) @id
   10  published Boolean @default(false)
   11  title     String
   12  User      User?   @relation(fields: [authorId], references: [id])
   13}
   14
   15model User {
   16  email String  @unique
   17  id    Int     @default(autoincrement()) @id
   18  name  String?
   19  Post  Post[]
   20}

   schema.prisma
   1datasource db {
   2  provider = "mysql"
   3  url      = env("DATABASE_URL")
   4}
   5
   6model Post {
   7  authorId  Int?
   8  content   String?
   9  id        Int     @default(autoincrement()) @id
   10  published Boolean @default(false)
   11  title     String
   12  User      User?   @relation(fields: [authorId], references: [id])
   13}
   14
   15model User {
   16  email String  @unique
   17  id    Int     @default(autoincrement()) @id
   18  name  String?
   19  Post  Post[]
   20}

5. Manually add the Draft view to the Prisma schema

You must manually add views to the Prisma schema.

1. Add a Draft model to the schema as shown:

   Note: The name of your view is case sensitive - if you created a view named draft in the database, you must create a model named draft in the Prisma schema.

   schema.prisma
   1datasource db {
   2  provider = "mysql"
   3  url      = env("DATABASE_URL")
   4}
   5
   6model Post {
   7  authorId  Int?
   8  content   String?
   9  id        Int     @default(autoincrement()) @id
   10  published Boolean @default(false)
   11  title     String
   12  User      User?   @relation(fields: [authorId], references: [id])
   13}
   14
   15model User {
   16  email String  @unique
   17  id    Int     @default(autoincrement()) @id
   18  name  String?
   19  Post  Post[]
   20}
   21
   + model Draft {
   +   title     String
   +   id        Int     @unique
   +   email     String
   +   published Boolean
   +  }

   schema.prisma
   1datasource db {
   2  provider = "postgresql"
   3  url      = env("DATABASE_URL")
   4}
   5
   6model Post {
   7  authorId  Int?
   8  content   String?
   9  id        Int     @default(autoincrement()) @id
   10  published Boolean @default(false)
   11  title     String
   12  User      User?   @relation(fields: [authorId], references: [id])
   13}
   14
   15model User {
   16  email String  @unique
   17  id    Int     @default(autoincrement()) @id
   18  name  String?
   19  Post  Post[]
   20}
   21
   + model Draft {
   +   title     String
   +   id        Int     @unique
   +   email     String
   +   published Boolean
   +  }

6. Generate Prisma Client

In this section, you will generate Prisma Client.

1. Add a generator block to your Prisma schema (typically added right below the datasource block):

   schema.prisma
   1generator client {
   2  provider = "prisma-client-js"
   3}

2. Run the following command to install and generate Prisma Client in your project:

   $npx prisma generate

Now you can use Prisma Client to send database queries in Node.js.

9. Validate the Draft view in a Node.js script

In the following section, you will use the drafts model property to return Post records that have not yet been published. To use the drafts model property:

1. Create a new file named index.js and add the following code to it:

   const { PrismaClient } = require('@prisma/client')
   
   const prisma = new PrismaClient({})
   
   async function main() {
     const sarahPosts = await prisma.user.create({
       data: {
         name: 'Sarah',
         email: 'sarah@prisma.io',
         Post: {
           create: [
             { title: 'My first post', published: false },
             { title: 'All about databases', published: true },
             { title: 'Prisma Day 2020', published: false },
           ],
         },
       },
     })
   
     const emilyPosts = await prisma.user.create({
       data: {
         name: 'Emily',
         email: 'emily@prisma.io',
         Post: {
           create: [
             { title: 'My first post', published: false },
             { title: 'All about databases', published: true },
             { title: 'Prisma Day 2020', published: false },
           ],
         },
       },
     })
   
     const drafts = await prisma.draft.findMany({})
   
     console.log(drafts)
   
     const filteredDrafts = await prisma.draft.findMany({
       where: {
         email: 'sarah@prisma.io',
       },
     })
   
     console.log(filteredDrafts)
   }
   
   main()
     .catch(e => {
       throw e
     })
     .finally(async () => {
       await prisma.$disconnect()
     })

   This example:

   • Creates two User records with three Post records each
   • Returns all Draft records from the view
   • Returns all Draft records from the view where the author's email is emily@prisma.io

2. Run the code with the following command:

   $node index.js

   The following output indicates that the view works as expected - the first query returns all drafts (Post records where published is false), and the second query returns drafts by emily@prisma.io only):

   /* ALL DRAFTS */
   ;[
     {
       title: 'My first post',
       id: 37,
       email: 'sarah@prisma.io',
       published: false,
     },
     {
       title: 'Prisma Day 2020',
       id: 39,
       email: 'sarah@prisma.io',
       published: false,
     },
     {
       title: 'My first post',
       id: 40,
       email: 'emily@prisma.io',
       published: false,
     },
     {
       title: 'Prisma Day 2020',
       id: 42,
       email: 'emily@prisma.io',
       published: false,
     },
   ][
     /* FILTERED DRAFTS */
     ({
       title: 'My first post',
       id: 37,
       email: 'sarah@prisma.io',
       published: false,
     },
     {
       title: 'Prisma Day 2020',
       id: 39,
       email: 'sarah@prisma.io',
       published: false,
     })
   ]