Via a very limited, free SQL tutorial from Codecademy:
BACKGROUND
SQL, Structured Query Language, is a programming language designed to manage data stored in relational databases. SQL operates through simple, declarative statements. This keeps data accurate and secure, and it helps maintain the integrity of databases, regardless of size.
Here’s an appendix of commonly used commands.
COMMANDS
ALTER TABLE
ALTER TABLE table_name
ADD column_name datatype;
ALTER TABLE
lets you add columns to a table in a database.