10. Constraints and Indexes

This module combines integrity rules and indexing strategy so you can design schemas that are both safe and fast.

Design Matrix

Need	Prefer
Unique row identity	PRIMARY KEY (usually surrogate identity)
Business uniqueness	UNIQUE constraint/index
Parent-child integrity	FOREIGN KEY + index the FK column
Domain/value control	NOT NULL, CHECK, DEFAULT
Fast lookups and joins	indexes (B-tree by default)

Lessons

• Primary and Foreign Keys
• Column and Table Constraints
• Index Strategy and Maintenance

What's Next

• Continue to 11. Date and Time Functions