Crud 1:25:17

Create

@app.posts("/posts")

Read

@app.get("/posts/{id}")
@app.get("/posts")

Update

@app.put("/posts/{id}")

Delete

@app.delete("/posts/{id}")

RUN

uvicorn app.main:app --reload

Databases

What is a database

• Database is a collection of organized data that can be easaly accessed and managed

DBMS

• We don't work or interact with databases directly
• Instead we make use of a software referred to as a Database Management System(DBMS)

Popular DBMS 2:25:30

Relational	NoSQL
MySQL	MongoDB
PostgreSQL	DynamoDB
Oracle	Oracle
SQL Server	SQL Server

Ralational Database & SQL

• Structured Query Languege(SQL) - Language used to cummunicate with DBMS

Postgres

• Each instance of postgres can be carved into multiple separete databases
• By Default every Postgres installation comes with one database already created called "postgres"
• This is important because Postgres requires you to specify the name of a database to make a connection. So there needs to always be one database

Tables

• A table represents a subject or event in an application

Columns Vs Rows

• A table is made up of columns and rows
• Each Column represents a different attribute
• Each row represents a different entry in the table

Postgres DataTypes

• Databases have datatypes just like any programming language | DataType | Postgres | Python | |----------|-------------------------|------------| | Numeric | int, decimal, precision | Int, float | | Text | Varchar, text | string | | Bool | boolean | boolean | | Sequence | array | list |

Primary Key

• Is a column or group of columns that uniquely identifies each row in a table
• Table can have one and only one primary key

Unique Constraints

• A UNIQUE constraint can be applied to any column to make sure every record has a unique value for that column

Null Constraints

• By default, when adding a new entry to a database, any column can be left blank. When a column is left blank, it has a null value
• If you need column to be properly filled in to create a new record, a NOT NULL constraint can be added to yhe column to ensure that the column is never left blank

Setting up postgres portable

Setting up postgres portable

Object Relational Mapper(ORM) 4:31:24

• Layer of obstraction that sits between the database and us
• We can perform all database operations through traditional python code. No more SQL!

What can ORMs Do

• Instead of manually defining tables in postgres, we can define our tables as python models
• Queries can be made exclusively through python code. No SQL is necessary

class Post(Base):
    __tablename__ = "posts"

    id = Column(Integer, primary_key=True, index=True)
    title = Column(String, index=True, nullable=False)
    content = Column(String, nullable=False)
    published = Column(Boolean)

db.query(models.Post).filter(models.Post.id == id).first()

SQLALCHEMY

• SQLALCHEMY is one of the most popular python ORMs
• It is stand-alone library and has no association with FastAPI, It can be used with any other python web frameworks or any python based application

Schema Models 5:29:56

• Schema/Pydantic Models define the structure of a request & response
• This ensure that when a user wants to create a post, the request will only go through if it has a "title" and "content" in the body

SQLALCHEMY Models

• Responsible for defining the columns of our "posts" table within postgres
• Is used to query, create, delete and update entries within the database