SQL to ER Diagram from CREATE TABLE

Your schema

CREATE TABLE statements (pg_dump --schema-only, mysqldump -d or sqlite3 .schema output)

--
-- PostgreSQL database dump (schema only)
--
SET statement_timeout = 0;
SET client_encoding = 'UTF8';
SELECT pg_catalog.set_config('search_path', '', false);

CREATE TYPE public.order_status AS ENUM ('basket', 'paid', 'shipped', 'refunded');

CREATE TABLE public.customers (
    id bigserial PRIMARY KEY,
    email text NOT NULL UNIQUE,
    name text NOT NULL,
    created_at timestamptz DEFAULT now() NOT NULL
);

CREATE TABLE public.addresses (
    id bigserial PRIMARY KEY,
    customer_id bigint NOT NULL REFERENCES public.customers(id) ON DELETE CASCADE,
    line1 text NOT NULL,
    town text NOT NULL,
    postcode varchar(8) NOT NULL
);

CREATE TABLE public.products (
    id bigserial PRIMARY KEY,
    slug text NOT NULL,
    name text NOT NULL,
    description text,
    CONSTRAINT products_slug_key UNIQUE (slug)
);

CREATE TABLE public.product_variants (
    id bigserial PRIMARY KEY,
    product_id bigint NOT NULL,
    sku varchar(32) NOT NULL UNIQUE,
    finish text NOT NULL,
    price_pence integer NOT NULL CHECK (price_pence > 0)
);

CREATE TABLE public.orders (
    id bigserial PRIMARY KEY,
    customer_id bigint NOT NULL,
    delivery_address_id bigint,
    status public.order_status DEFAULT 'basket' NOT NULL,
    placed_at timestamptz
);

CREATE TABLE public.order_items (
    order_id bigint NOT NULL,
    variant_id integer NOT NULL,
    qty integer NOT NULL DEFAULT 1,
    price_pence integer NOT NULL,
    PRIMARY KEY (order_id, variant_id)
);

CREATE TABLE public.payments (
    id bigserial PRIMARY KEY,
    order_id bigint NOT NULL,
    provider text NOT NULL,
    amount_pence integer NOT NULL,
    CONSTRAINT payments_order_id_key UNIQUE (order_id)
);

CREATE TABLE public.reviews (
    id bigserial PRIMARY KEY,
    product_id bigint NOT NULL REFERENCES public.products(id),
    customer_id bigint REFERENCES public.customers(id) ON DELETE SET NULL,
    stars smallint NOT NULL,
    body text
);

ALTER TABLE public.customers OWNER TO hartley;
COMMENT ON TABLE public.orders IS 'One row per basket; status moves to paid at checkout';

ALTER TABLE ONLY public.product_variants
    ADD CONSTRAINT product_variants_product_id_fkey FOREIGN KEY (product_id) REFERENCES public.products(id) ON DELETE CASCADE;
ALTER TABLE ONLY public.orders
    ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES public.customers(id);
ALTER TABLE ONLY public.orders
    ADD CONSTRAINT orders_delivery_address_id_fkey FOREIGN KEY (delivery_address_id) REFERENCES public.addresses(id) ON DELETE SET NULL;
ALTER TABLE ONLY public.order_items
    ADD CONSTRAINT order_items_order_id_fkey FOREIGN KEY (order_id) REFERENCES public.orders(id) ON DELETE CASCADE;
ALTER TABLE ONLY public.order_items
    ADD CONSTRAINT order_items_variant_id_fkey FOREIGN KEY (variant_id) REFERENCES public.product_variants(id);
ALTER TABLE ONLY public.payments
    ADD CONSTRAINT payments_order_id_fkey FOREIGN KEY (order_id) REFERENCES public.orders(id);

CREATE INDEX addresses_customer_id_idx ON public.addresses USING btree (customer_id);
CREATE INDEX orders_customer_id_idx ON public.orders USING btree (customer_id);
CREATE INDEX product_variants_product_id_idx ON public.product_variants USING btree (product_id);

CREATE FUNCTION public.touch() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN NEW.placed_at := now(); RETURN NEW; END;
$$;

ER diagram

Highlight a table

Crow's foot: many rows on this side
Bar: exactly one
Dashed line and circle: optional (the foreign key can be null)

Mermaid

Mermaid erDiagram

DBML

DBML (dbdiagram.io)

Skipped statements

Line	Why	Statement

Columns per table

What it does

Draws an entity relationship diagram from CREATE TABLE and ALTER TABLE statements, flags foreign keys with no index and exports Mermaid and DBML.

PostgreSQL, MySQL and SQLite DDL, including pg_dump and mysqldump output
Foreign keys inline, as table constraints and from ALTER TABLE
One-to-one, one-to-many and optional relations read from UNIQUE and NULL
Foreign keys with no index, type mismatches and tables with no primary key flagged

Private by design

Everything happens in your browser. Nothing you type, paste or upload is sent anywhere, and it keeps working offline once the page has loaded.

What you get

An SVG or PNG diagram, schema checks, Mermaid and DBML, with a Copy and a Download button on every result.

SQL
ER diagram
PostgreSQL
MySQL

Why it matters

Schemas live in migration files and dump output, and reading forty CREATE TABLE statements to work out how the tables join is slow. Diagram tools usually want you to redraw the schema by hand or connect them to the database.

This tool reads the DDL itself. It splits the script into statements (respecting quotes, comments and function bodies), reads columns, primary keys, unique constraints and foreign keys wherever they're declared, including ALTER TABLE ... ADD CONSTRAINT lines from pg_dump, and works out each relation's cardinality: a unique foreign key is one-to-one, a nullable one is optional. It then lays the tables out, draws crow's-foot connectors and checks the schema for problems a review would catch: foreign keys with no index on the referencing columns (slow joins and slow deletes on the parent), a foreign key column whose type doesn't match the key it points at, and tables without a primary key. Nothing is sent anywhere.

How it works

InputCREATE TABLE statements or a schema dump
In your browserTables, keys and cardinality read from the DDL
OutputA diagram, schema checks, Mermaid and DBML

Where it fits in a designer's workflow

Plan
Design
Build
Test
Launch

Understanding or documenting a database before you change it.

By the numbers

Read by this tool from its sample pg_dump: 8 tables, 36 columns and 9 relationships, with 5 schema checks raised and 6 statements skipped (settings, ownership, comments and a function). Foreign keys are counted on the table that holds them. Source: PostgreSQL: CREATE TABLE; PostgreSQL: foreign keys and indexes.

Show the numbers as a table

Table	Columns	Foreign keys
customers	4	0
addresses	5	1
products	4	0
product_variants	5	1
orders	5	2
order_items	4	2
payments	4	1
reviews	5	2

How to use it

Paste your CREATE TABLE statements, or the output of pg_dump --schema-only, mysqldump -d or sqlite3 .schema.
Read the diagram; click a table name in the list to centre it.
Work through the schema checks.
Download the diagram, or copy the Mermaid or DBML into your docs.

FAQ

Which databases does it understand?

PostgreSQL, MySQL and MariaDB, and SQLite DDL. It detects the dialect from the syntax, such as bigserial, AUTO_INCREMENT or backtick quoting. Statements it doesn't model, like functions, grants and comments, are listed as skipped.

How is one-to-one decided?

A foreign key whose columns are also a primary key or have a UNIQUE constraint can only match one row per parent, so it's drawn one-to-one. A nullable foreign key is drawn as optional.

Why does it want an index on foreign keys?

PostgreSQL doesn't create one automatically. Without it, joins from the child side scan the table, and deleting or updating a parent row has to scan the child table to check the constraint. MySQL InnoDB creates one for you.

Can I use the Mermaid output on GitHub?

Yes. Paste it into a ```mermaid code block in a README or issue and GitHub draws it.

Is my schema uploaded?

No. It's parsed and drawn in your browser.

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SQL Schema to ER Diagram