Primary keys - the basics
Single-column primary keys
Multicolumn primary keys
Auto-increment columns and sequences
Instruction
Okay. Note that in some databases, you will encounter the keyword AUTO_INCREMENT instead of IDENTITY. The AUTO_INCREMENT is not used as a data type. It is an additional keyword that you put after the name of the type. The table movie from an earlier exercise could be created like this:
CREATE TABLE movie (
id INTEGER AUTO_INCREMENT (3,5),
title varchar(64),
year int,
genre varchar(20)
);
If you omit the AUTO_INCREMENT parameters, then the auto incremening numbers start with 1 and increment by 1. Like here:
CREATE TABLE movie (
id INTEGER AUTO_INCREMENT,
title varchar(64),
year int,
genre varchar(20)
);
Exercise
Create the table cinema again, but use the keyword AUTO_INCREMENT this time.
Include the following columns:
cinema_id- integer with consecutive numbers automatically generated, it's also the primary key,name- up to 30 characters,city- up to 30 characters.
Stuck? Here's a hint!
Type
CREATE TABLE cinema (
cinema_id INTEGER AUTO_INCREMENT PRIMARY KEY,
name varchar(30),
city varchar(30)
);
