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Primary keys - the basics
2. Primary keys - Syntax
Single-column primary keys
Multicolumn primary keys
Auto-increment columns and sequences


Okay, have you noticed the new element in the code? You should be familiar with the instruction:

   id int PRIMARY KEY,
   title varchar(64),
   year int

It will create a table called movie with the columns specified in the parentheses. There, we provide column names with their types. However, after the part id int, we put the following piece of information:


In this part of the course, we're going to examine primary keys closely. What are they? A primary key is a set of columns which is used to identify a given row in the table. Sounds too vague? Don't worry, we're going to explain that soon!


We've put some information into the table movie. Take a close look at the contents of the table.

Examine the column id which is the primary key. Each id is unique - the same number only appears once.

Apart from that, we do not have id 7. That's correct - primary keys do not need to follow any specific order. If number 7 is missing, nothing particular happens.