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LESSON 16

SQL (Core) - Creating tables

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SQL Lesson 16: Creating tables

Before inserting data, you must establish relational table schemas using the CREATE TABLE Data Definition Language (DDL) query.

1. CREATE TABLE Syntax & Constraints

Every column requires a name, data type (INTEGER, TEXT, REAL, BOOLEAN, DATETIME), and optional schema enforcement constraints: 

CREATE TABLE IF NOT EXISTS database_courses (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  title TEXT NOT NULL UNIQUE,
  category TEXT DEFAULT 'General',
  rating REAL CHECK (rating >= 0 AND rating <= 5),
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

2. Schema Constraint Breakdown

  • PRIMARY KEY: Guarantees row uniqueness and speeds up table lookups.
  • NOT NULL: Rejects insertions missing this required attribute.
  • UNIQUE: Prevents duplicate emails, usernames, or titles.
  • DEFAULT: Automatically populates timestamps or fallbacks if omitted.
  • CHECK: Validates value boundaries before writing to disk.

🗄️ Schema Explorer SELECTABLE

› movies
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🎯 Exercises Checklist:

☐ 1. Create a new table named Database with columns: Name (TEXT), Version (FLOAT), Download_count (INTEGER)
☐ 2. Create a new table named Users with columns: id (INTEGER PRIMARY KEY), username (TEXT NOT NULL), email (TEXT UNIQUE)
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