Page 50 - SQL

LastName VARCHAR(20) NOT NULL,
PhoneNumber VARCHAR(10) NOT NULL,
CityID INT FOREIGN KEY REFERENCES Cities(CityID)
);

Here could you find a database diagram.

The column CityID of table Employees will reference to the column CityID of table Cities. Below you
could find the syntax to make this.

CityID INT FOREIGN KEY REFERENCES Cities(CityID)

Value Meaning

CityID Name of the column

int type of the column

FOREIGN KEY Makes the foreign key (optional)

REFERENCES Makes the reference
Cities(CityID) to the table Cities column CityID

Important: You couldn't make a reference to a table that not exists in the database. Be source to
make first the table Cities and second the table Employees. If you do it vise versa, it will throw an
error.

Create a Temporary or In-Memory Table

PostgreSQL and SQLite

To create a temporary table local to the session:

CREATE TEMP TABLE MyTable(...);

https://riptutorial.com/ 32