DBML (database markup language) is a simple, readable DSL language designed to define database structures.

• It is simple, flexible and highly human-readable
• It is database agnostic, focusing on the essential database structure definition without worrying about the detailed syntaxes of each database
• Comes with a free, simple database visualiser at dbdiagram.io

(Coming soon): A dbml-to-sql generator to generate SQL from .dbml file

Example of a database definition of a simple blogging site:

Table users {
  id integer [primary key]
  username varchar(255) [not null]
  display_name varchar(255)
  role UserRole [not null]
  created_at timestamp [default: 'now()']

  indexes {
    created_at,
    username [unique]
  }
}

Table posts {
  id integer [auto increment, primary key]
  title varchar(255) [not null]
  body text
  user_id integer [ref: >users.id] // inline references
  cat_id integer [ref: >cats.id]
  status PostStatus
}

Table cats {
  id integer [auto increment, primary key]
  slug varchar(255) [unique]
  name varchar(255)
}

Ref: posts.user_id > users.id // many-to-one
Ref: cats.id < posts.cat_id   // one-to-many

Enum UserRole {
  admin
  editor
  viewer
}

Enum PostStatus {
  public
  private
  draft
}

Not quite. Despite its name (data "definition" language), DDL is designed mainly to help physically create, modify or remove tables, not to define them.

DDL also comes with a few more drawbacks:

• It is hard to read, especially when trying to add multiple column/table settings together.
• It is database specific (Oracle vs PostgreSQL vs MySQL, etc)
• Since it is imperative (vs declarative), to fully reconstruct a table definition you have to trace through all the code (instead of focusing on just 1 single section).

1. Go to dbdiagram.io
2. Type up your DBML code
3. Go to Export > SQL (choose your DB)

DBML supports defining the following:

• Table Definition
  • Table Alias
  • Table Notes (coming soon)
  • Table Settings
• Column Definition
  • Column Settings
  • Default Value (NEW)
  • Index Definition (coming soon)
    • Index Settings (coming soon)
• Relationships & Foreign Key Definitions
  • Many-to-many relationship
• Comments
• Metadata Notes
• Enum Definition
• TableGroup, ColorScheme (coming soon)
• Syntax Consistency
• Community Contributions

Table table_name {
    column_name column_type [column_settings]
}

• title of database table is listed as table_name
• name of the column is listed as column_name
• type of the data in the column listed as column_type
• list is wrapped in curly brackets {}, for indexes, constraints and table definitions.
• settings are wrapped in square brackets []
• string value is be wrapped in a single quote as 'string'
• column_name is stated in just plain text
• (coming soon) column_name can be wrapped in a double quote as "column_name"

Table Alias: You can alias the table, and use them in the references later on

Table very_long_user_table as U {
  ...
}

Ref: U.id < posts.user_id

Table Notes (coming soon): You can add notes to the table, and refer to them in the visual plane

Table Settings: Settings are all defined within square brackets: [setting1: value1, setting2: value2, setting3, setting4]

Each setting item can take in 2 forms: Key: Value or keyword, similar to that of Python function parameters.

• color: <color_code>: change the table header color (coming soon)

  Example, [color: blue]

Column Settings: Each column can take have optinal settings, defined in square brackets like:

Table buildings {
    ...
    address varchar(255) [unique, not null, note: "to include unit number"]
    id integer [ pk, unique, default: 123, note: "Number" ]
}

The list of column settings you can use:

• primary key or pk: mark a column as primary key. For composite primary key, refer to the Indexes section
• null or not null: mark a column null or not null
• unique: mark the column unique
• note: "string to add notes": add a metadata note to this column
• default: some_value: set a default value of the column, please refer to the Default Value section below (coming soon)
• auto increment: mark the column as auto increment (coming soon)

Default Value (NEW): You can set default value as:

• number value starts blank: default: 123 or default: 123.456
• string value starts with single quotes: default: 'some string value'
• expression value is wrapped with parenthesis: default: `now() - interval '5 days'`
• boolean (true/false/null): default: false or default: null

Example,

Table users {
    id integer [primary key]
    username varchar(255) [not null, unique]
    full_name varchar(255) [not null]
    gender varchar(1) [default: 'm']
    created_at timestamp [default: `now()`]
    rating integer [default: 10]
}

Index Definition (coming soon): Indexes allow users to quickly locate and access the data.

Table bookings {
    id integer [primary key]
    country varchar
    booking_date date
    created_at timestamp

    indexes {
        created_at [note: 'Date']
        booking_date
        (country, booking_date) [unique]
        booking_date [type: 'hash']
	    (`id*2`)
	    (`id*3`,`getdate()`)
	    (`id*3`,id)
    }
}

Index Settings (coming soon)

• type: type of index (btree, gin, gist, hash depending on DB)
• name: name of index
• unique: unique index

Relationships are used to define foreign key constraints between tables.

Table posts {
    id integer [primary key]
    user_id integer [ref: > users.id] // many-to-one
}

// or this
Table users {
    id integer [ref: < posts.user_id, ref: < reviews.user_id] // one to many
}

// The space after '<' is optional

There are 3 types of relationships: one-to-one, one-to-many, and many-to-one

• <: one-to-many. E.g: users.id < posts.user_id
• >: many-to-one. E.g: posts.user_id > users.id
• -: one-to-one. E.g: users.id - user_infos.user_id

In DBML, there are 3 syntaxes to define relationships:

//Long form
Ref name_optional {
  table1.field1 < table2.field2
}

//Short form:
Ref name_optional: table1.field1 < table2.field2

// Inline form
Table posts {
    id integer
    user_id integer [ref: > users.id]
}

Many-to-many relationship

For many-to-many relationship, we don't have a syntax for it as we believe it should be represented as 2 many-to-one relationships. For more information, please refer to https://www.holistics.io/blog/dbdiagram-io-many-to-many-relationship-diagram-generator-script/

You can comment in your code using //, so it is easier for you to review the code later.

Example,

// order_items refer to items from that order

You can add notes to your field, so you can easily refer to it when hovering over the field in the diagram canvas.

column_name column_type [note: 'replace text here']

Example,

Table orders {
    status varchar [
    note: '
    💸 1 = processing, 
    ✔️ 2 = shipped, 
    ❌ 3 = cancelled,
    😔 4 = refunded
    ']
}

Enum allows users to define different values of a particular column. When hovering over the column in the canvas, the enum values will be displayed.

enum job_status {
    created [note: 'Waiting to be processed']
    running
    done
    failure
}

Table jobs {
    id integer
    status job_status
}

DBML is the standard language for database and the syntax is consistent to provide clear and extensive functions.

• curly brackets {}: grouping for indexes, constraints and table definitions
• square brackets []: settings
• forward slashes //: comments
• column_name is stated in just plain text
• single quote as 'string': string value
• double quote as "column_name": quoting variable (coming soon)
• backtick `: function expression (coming soon)

• Emacs Mode for DBML (Contributed by ccod): https://github.com/ccod/dbd-mode