A database holds one or more tables. You can think of a database table like a spreadsheet or csv file that holds structured data.
The data type specifies what type of data the column can hold. For a complete reference of all the data types available in MySQL, go to our complete Data Types reference.
Primary Keys and Auto Increment Fields
Each table in a database should have a primary key field.
A primary key is used to uniquely identify the rows in a table. Each primary key value must be unique within the table. Furthermore, the primary key field cannot be null because the database engine requires a value to locate the record.
- SQL for Beginners article.