Tables, Rows, Columns, and Keys

A Table Is Rows and Columns

Data in a relational database lives in tables that have rows and columns. One row is one record, and one column is one attribute. The primary key is the column that uniquely identifies each row. In the customers table in the panel on the right, that column is id.

GOAL

Explain what a primary key is and why it uniquely identifies a row.

To identify exactly Alice's row and no other, which column should you filter on?

CHECK IT

customers

6 rows × 4 cols

Highlighted row / column

customers6 rows × 4 cols

id	name	city	referred_by
1	Alice	Tokyo	NULL
2	Bob	Osaka	1
3	Carol	Tokyo	2
4	Dave	Osaka	1
5	Erin	Nagoya	NULL
6	Frank	NULL	3

Data in a relational database lives in tables of rows and columns.