Table Workshop - welcome to the scriptorium!
Welcome back, @name! This time we descend into the scriptorium - the heart of the Library, where new shelves are made. So far you have learned to read scrolls. Today I will teach you to build the shelves themselves - that is, tables.
From reading to creating
The commands you learned earlier (SELECT, WHERE, ORDER BY) were used to retrieve data. They belong to a group called DML (Data Manipulation Language). Now we enter the world of DDL (Data Definition Language) - the language with which we define the structure of the Library.
DDL lets us:
- create new shelves (CREATE TABLE),
- rebuild existing shelves (ALTER TABLE),
- drop entire shelves (DROP TABLE).
What is a table as a construction?
Think of a shelf you are only just designing. Before you place a single scroll on it, you must decide:
- how many fields (columns) it will have,
- what kind of data will go into each field (types),
- what rules they must meet (constraints).
That is exactly what CREATE TABLE does - it draws the plan of the shelf before any data appears on it.
Plan of this location
In the scriptorium you will learn to:
- create tables with CREATE TABLE,
- choose data types (INT, VARCHAR, DATE, DECIMAL, ENUM...),
- give columns constraints (PRIMARY KEY, NOT NULL, DEFAULT, UNIQUE...),
- rebuild tables with ALTER TABLE,
- remove them with DROP TABLE.
Grab a chisel and stylus, scribe - we will build your first shelf!