Background

SQL sublanguage: DDL (Data Definition Language)

Let's say we created the following table:

id	firstname
1	'Kevin'
2	'Brian'
3	'Charles'

The site_user table when it was created, forgot to add the 'lastname' column.

We could go about solving this in 2 different ways:

• We could remove the table completely and create the table again with the correct number of columns
• We can use the ALTER keyword to add a new column to the existing table. (This is what we will be looking at for this lab) The ALTER keyword allows us to add / remove columns and constraints on an existing table. The syntax for the ALTER keyword is different depending on what we want to achieve:
  • Adding a column:
    • sql ALTER TABLE table_name ADD column_name data_type [constraint];
  • Removing a column:
    • sql ALTER TABLE table_name DROP column_name;

NOTE: the [] in the "Adding a column" syntax means that the constraint is optional

Additional reference material if needed: https://www.w3schools.com/sql/sql_alter.asp

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Lab

Problem 1

site_user table

id	firstname
1	'Kevin'
2	'Brian'
3	'Charles'

Problem 1: Use the ALTER keyword to add a "lastname" column to the "site_user" table, of type varchar(100).