Use the Sequelize ORM to access a PostgreSQL databases Module#61

Question 1

How can we install the sequelize package via npm

Answer 1

First run npm init -y

npm install sequelize

Question 2

What is the first step in using sequelize?

Answer 2

First make a connection to the DB as follows, update the default fields;

const user = ''
const host = 'localhost'
const database = ''
const password = ''
const port = ''

Question 3

When you specify “dialect” what are you telling Sequelize?

Answer 3

On this line we’re telling Sequelize what kind of database to expect.

Question 4

What is the syntax for creating a new Sequelize object instance?

Answer 4

const sequelize = new Sequelize(database, user, password, {
  host,
  port,
  dialect: 'postgres',
  logging: false
})

Question 5

What do you need to do in order to manipulate a table

Answer 5

You need to create a model

Question 6

How can we get data out of the table?

Answer 6

Use the .findAll( ) method

Dog.findAll()

Question 7

When using the findAll( ) method it will return a list of rows. How can we access them?

Answer 7

Assign it to a variable called results:
const results = await Dog.findAll( )

Question 8

How can we limit the columns we retrieve?

Answer 8

By passing an object with the attributes array:
Dog.findAll({
attributes: [‘age’]
})

Question 9

What if you want to narrow the results even more, for example all dogs aged *

Answer 9

Add a WHERE clause, with your age parameter:

Dog.findAll({
  where: {
    age: 8,
  }
})

Question 10

To get all dogs equal or higher to 5?

Answer 10

Use Op.gte

Dog.findAll({
  where: {
    age: {
      [Op.gte]: 5,
    }
  }
})

Question 11

How is new data entered into our DB?

Answer 11

Using the .create( ) method

Question 12

How do we update the data we already have?

Answer 12

Surprise! Using the .update( ) method. But it needs to get attached to the proper object you want to update.

Example:

Dog.update({
  age: 9
}, {
  where: {
    name: 'Roger'
  }
})

Question 13

What happens when we remove the where property?

Answer 13

It will update all rows instead of just a single row.