Which SQL database dialects are supported?

The converter supports *PostgreSQL, MySQL, MariaDB, SQLite, Oracle, and MS SQL ServerCREATE TABLE syntax.

How does the tool handle columns without NOT NULL?

If *'Allow Nullable Types'is active, non-required fields are generated as *type: ['string', 'null']or type: ['integer', 'null'].

Can I convert multiple tables in a single script?

Yes, pasting multiple CREATE TABLE statements generates a modular root schema with nested definitions (Draft 7) or $defs (Draft 2020-12).

Are primary keys automatically marked as required?

Yes, any column designated as PRIMARY KEY is automatically added to the required array.

Is this JSON Schema output compatible with Ajv, Fastify, and OpenAPI?

Yes, generated schemas follow *100% standard JSON Schema Draft 7 / Draft 2020-12 specificationscompatible with Ajv and OpenAPI 3.x.

What happens if my SQL has syntax errors or unsupported statements?

The integrated linter reports the exact issue and offers a *⚡ 1-Click Auto-Fixbutton for common SQL syntax errors.

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DEVELOPER TOOLSE-E-A-T

🗄️

SQL to JSON Schema Converter

Convert PostgreSQL, MySQL, and SQLite CREATE TABLE DDL scripts into standard JSON Schema specifications with required validation rules.

🗄️

JSON Schema Specification:

Include SQL Comments as Descriptions:

Allow Nullable Types (e.g. ['string', 'null']):

Valid Syntax

📥 SQL CREATE TABLE Script

📤 JSON Schema

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://example.com/schemas/users.json",
  "title": "users",
  "type": "object",
  "properties": {
    "id": {
      "type": "string",
      "format": "uuid"
    },
    "username": {
      "type": "string",
      "maxLength": 50,
      "description": "Unique user handle"
    },
    "email": {
      "type": "string",
      "maxLength": 255,
      "description": "Primary contact email"
    },
    "age": {
      "type": [
        "integer",
        "null"
      ]
    },
    "is_active": {
      "type": "boolean"
    },
    "metadata": {
      "type": [
        "object",
        "null"
      ]
    },
    "created_at": {
      "type": "string",
      "format": "date-time"
    }
  },
  "required": [
    "id",
    "username",
    "email",
    "is_active",
    "created_at"
  ],
  "additionalProperties": false
}

Presets:

Quick Answer & Understanding Your Result

Source: JSON Schema Official Specification & Draft Standards

An SQL to JSON Schema Converter transforms relational database CREATE TABLE DDL statements into standardized JSON Schema specifications, automatically mapping SQL data types, constraints, and field descriptions for API contract validation.

Core Schema Transformation Features

Deterministic SQL Type Mapping: Accurately maps VARCHAR, UUID, INT, DECIMAL, BOOLEAN, TIMESTAMP, and JSONB to JSON Schema primitives and formats (date-time, uuid).
Required Constraint Extraction: Automatically identifies NOT NULL and PRIMARY KEY modifiers to populate the required: [...] array.
Multi-Table & Definition Scoping: Bundles multiple CREATE TABLE declarations into modular definitions (Draft 7) or $defs (Draft 2020-12).
Embedded Comments as Descriptions: Preserves column comments as JSON Schema description properties for self-documenting OpenAPI specs.

Practical Engineering Workflows

API Payload Validation: Generating JSON validation schemas directly from existing production database tables.
OpenAPI & Swagger Generation: Bootstrapping request/response body schemas for RESTful and microservice APIs.

Paste your SQL DDL statements into the editor above to generate your complete JSON Schema definition in 0ms.

Formula & Calculation Logic

Technical Specification & AST

Mathematical Formula

SQL DDL AST → $schema, type: "object", properties, required

Transformation pipeline:

Parses relational table DDL AST, infers column datatypes and non-null constraints, and emits compliant JSON Schema structure.

Step-by-Step Guide

Paste SQL CREATE TABLE Script

Paste PostgreSQL, MySQL, or SQLite DDL script into the left code editor.

Choose Schema Draft Version

Select between JSON Schema Draft 7 (Default) or modern Draft 2020-12.

Configure Nullability Options

Toggle nullable type unions (e.g. ['string', 'null']) and comment inclusion.

Copy JSON Schema Code

Click 1-Click Copy to grab the formatted JSON Schema for your validation pipeline.

Worked Examples Table

Example	Input Values	Calculated Result	Explanation
Users Table with UUID, Email, JSONB & Timestamp	Input: CREATE TABLE users ( id UUID PRIMARY KEY, username VARCHAR(50) NOT NULL, email VARCHAR(255) NOT NULL, age INT NULL, is_active BOOLEAN NOT NULL DEFAULT true, created_at TIMESTAMP NOT NULL );, Schema Version: draft-07, Include Descriptions: true, Allow Null By Default: true	{ "$schema": "http://json-schema.org/draft-07/schema#", "title": "users", "type": "object", "properties": { "id": { "type": "string", "format": "uuid" }, "username": { "type": "string", "maxLength": 50 }, "email": { "type": "string", "maxLength": 255 }, "age": { "type": ["integer", "null"] }, "is_active": { "type": "boolean" }, "created_at": { "type": "string", "format": "date-time" } }, "required": ["id", "username", "email", "is_active", "created_at"] }	Mapped SQL datatypes to exact JSON Schema formats with non-null constraint validation.
E-Commerce Orders & Items (Multi-Table)	Input: CREATE TABLE orders ( order_id VARCHAR(36) PRIMARY KEY, customer_id VARCHAR(36) NOT NULL, total_amount DECIMAL(10, 2) NOT NULL, status VARCHAR(20) NOT NULL, created_at TIMESTAMP NOT NULL ); CREATE TABLE order_items ( item_id SERIAL PRIMARY KEY, order_id VARCHAR(36) NOT NULL, sku VARCHAR(50) NOT NULL, quantity INT NOT NULL, unit_price DECIMAL(10, 2) NOT NULL );, Schema Version: draft-07, Include Descriptions: true, Allow Null By Default: true	Accurate Operational Result	Provides instant quantitative evaluation for comparative practical analysis.

Frequently Asked Questions

Evidence-Based Methodology & Authoritative References

References & Methodology

JSON Schema Official Specification & Draft Standards

View Reference

ANSI/ISO SQL Database Language Standard (ISO/IEC 9075)

View Reference

Calculation Standard & Formulation

Standard: ISO / W3C / IETF Authoritative Domain Standard

Formula: SQL DDL AST → $schema, type: "object", properties, required

Last Reviewed: August 21, 2026

Authoritative Sources & Peer Review

Primary Source: JSON Schema Official Specification & Draft Standards

Reference Document: ANSI/ISO SQL Database Language Standard (ISO/IEC 9075)

Computation Privacy: 100% client-side 0ms computation, zero data retention

Technical Standards & Execution Scope

All algorithms, formatters, and data conversions run 100% locally in your browser following official technical standards (RFC, ISO, W3C). Output should be verified prior to mission-critical production deployment.

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