SQL Data Types

Picking the right type makes queries faster, indexes smaller, and bugs less likely. The big families exist in every major engine — only the names differ.

Integers

Decimals & floats

• DECIMAL(p, s) — exact, base-10. Use for money: DECIMAL(10, 2).
• FLOAT / DOUBLE — binary IEEE-754. Fast but lossy — never for money.

Strings

Dates & times

• DATE — Y-M-D only.
• TIME — H:M:S only.
• DATETIME / TIMESTAMP — both. PG / SQL Server: TIMESTAMPTZ stores zone.

Binary & JSON

• BLOB / BYTEA — raw bytes.
• JSON / JSONB — structured data; JSONB in Postgres is indexable.
• UUID — 16-byte global identifier (PG native; emulate with CHAR(36) elsewhere).

Example

CREATE TABLE demo (
  id INT,
  name VARCHAR(80),
  price DECIMAL(10,2),
  notes TEXT,
  created_at DATETIME
);

Exercise

Test yourself