How do types differ between MySQL, PostgreSQL, and SQLite?

Tables are stored internally with shared logical types (INTEGER, DECIMAL, VARCHAR, etc.) and only converted to each database's real types when you generate DDL. For example, BOOLEAN becomes INTEGER on SQLite (which has no boolean type), and an auto-increment primary key becomes AUTO_INCREMENT on MySQL, SERIAL on PostgreSQL, and INTEGER PRIMARY KEY AUTOINCREMENT on SQLite.

What happens to NOT NULL, UNIQUE, and the default value when a column is marked PK?

A primary key is NOT NULL and UNIQUE by definition, so once a column is marked PK, its NOT NULL/UNIQUE/default settings are ignored — it's emitted as just "TYPE PRIMARY KEY" (plus AUTO_INCREMENT/SERIAL/etc. if auto-increment is on).

How does generating from JSON handle nested data?

A top-level property whose value is an array of objects is automatically split into its own table with a foreign key back to the parent (e.g. an order and its line items). A nested plain object becomes a JSON-typed column instead. Nesting deeper than one level isn't split automatically, so adjust those cases by hand.

Can I use the generated DDL directly in a production migration?

This tool is meant as a starting point for table design or a review artifact — it doesn't generate indexes, CHECK constraints, character sets/collations, or partitioning, which real deployments usually need. Always review the output and adjust it before using it in production.

DB Design

DDL Builder

Design tables visually and generate CREATE TABLE statements (MySQL / PostgreSQL / SQLite) together with an ER diagram. You can also paste a JSON sample to infer columns automatically. Everything runs in your browser — nothing you enter is sent anywhere.

Generate from JSON (optional)

Table name

JSON sample (object or array)

Table design

Relations (foreign keys)

DDL output

Dialect

CREATE TABLE statements

ER diagram preview

Articles for this tool

Introduction

2026-08-03

How CREATE TABLE Generation From a Visual Table Design Works | DDL Builder

A look inside DDL Builder, which turns a visually designed table into CREATE TABLE statements and an ER diagram. Covers the MySQL/PostgreSQL/SQLite type-mapping rules and the column-inference algorithm used for JSON samples.

Use Case

2026-08-04

CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints

A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.

DDL Builder

Guide

FAQ

Use cases

Notes