Use smallest data type that fits your data. SMALLINT (2 bytes) vs INTEGER (4 bytes) saves 50% storage. Index columns with constraints for faster queries.

Smaller data types = less storage and faster queries

SMALLINT (2 bytes) vs INTEGER (4 bytes) saves 50%

VARCHAR for variable text, CHAR only for fixed codes

Index columns used in WHERE and JOIN clauses

Perf Impact: Functions/conversions in WHERE: No index use. Move to computed columns

Using FLOAT for money (rounding errors)

Forgetting NOT NULL on required fields

Using VARCHAR for dates (no validation)

Missing CHECK constraints for business rules

Using INTEGER when SMALLINT would suffice