SQL Data Definition Language (DDL)

SQL Data Definition Language (DDL)

This guide covers the essential DDL commands used for defining and managing database structures, including creating, modifying, and deleting tables.

Table of Contents:

1. CREATE - Creating Tables
2. ALTER - Modifying Table Structure
3. DROP - Removing Tables

/* ============================================================================== 
   CREATE
=============================================================================== */

/* Create a new table called persons 
   with columns: id, person_name, birth_date, and phone */
CREATE TABLE persons (
    id INT NOT NULL,
    person_name VARCHAR(50) NOT NULL,
    birth_date DATE,
    phone VARCHAR(15) NOT NULL,
    CONSTRAINT pk_persons PRIMARY KEY (id)
)

/* ============================================================================== 
   ALTER
=============================================================================== */

-- Add a new column called email to the persons table
ALTER TABLE persons
ADD email VARCHAR(50) NOT NULL

-- Remove the column phone from the persons table
ALTER TABLE persons
DROP COLUMN phone

/* ============================================================================== 
   DROP
=============================================================================== */

-- Delete the table persons from the database
DROP TABLE persons

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