Introduction
Automatically-created indexes
SQL index best practices
Instruction
Okay, it's time you created a UNIQUE INDEX by yourself. Here's the syntax:
CREATE UNIQUE INDEX index_name ON table_name(column_name);
Exercise
We've got the following definition of the invoice table:
CREATE TABLE invoice ( id integer PRIMARY KEY, number varchar(18) UNIQUE, qr_code_url varchar(512), issue_date date, customer_id integer, amount decimal(10, 2), currency char(3) );
The company wants to test a new feature where every invoice has a UNIQUE QR code for quicker access. Note that we've added a column named qr_code_url.
Your task is to create a UNIQUE index named unique_qr_url on the column qr_code_url.
Stuck? Here's a hint!
Remember to use a UNIQUE keyword.
