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DBML - Full Syntax Docs

DBML (database markup language) is a simple, readable DSL language designed to define database structures. This page outlines the full syntax documentations of DBML.

Example​

Table users {
  id integer
  username varchar
  role varchar
  created_at timestamp
}

Table posts {
  id integer [primary key]
  title varchar
  body text [note: 'Content of the post']
  user_id integer
  created_at timestamp
}

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

Project Definition​

You can give overall description of the project.

Project project_name {
  database_type: 'PostgreSQL'
  Note: 'Description of the project'
}

Schema Definition​

A new schema will be defined as long as it contains any table or enum.

For example, the following code will define a new schema core along with a table user placed inside it

Table core.user {
  ...
}

Public Schema​

By default, any table, relationship, or enum definition that omits schema_name will be considered to belong to the public schema.

Table Definition​

// table belonged to default "public" schema
Table table_name {
  column_name column_type [column_settings]
}

// table belonged to a schema
Table schema_name.table_name {
  column_name column_type [column_settings]
}
  • (Optional) title of database schema is listed as schema_name. If omitted, schema_name will default to public
  • 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
    • supports all data types, as long as it is a single word (remove all spaces in the data type). Example, JSON, JSONB, decimal(1,2), etc.
  • 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 can be stated in just plain text, or 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​

You can add notes to the table, and refer to them in the visual plane.

Table users {
  id integer
  status varchar [note: 'status']

  Note: 'Stores user data'
}

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.

  • headercolor: <color_code>: change the table header color.

Example,

Table users [headercolor: #3498DB] {
  id integer [primary key]
  username varchar(255) [not null, unique]
}

Column Definition​

Column Settings​

Each column can take have optional 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:

  • note: 'string to add notes': add a metadata note to this column
  • 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
  • default: some_value: set a default value of the column, please refer to the 'Default Value' section below
  • increment: mark the column as auto-increment

Note: You can use a workaround for un-supported settings by adding the setting name into the column type name, such as id “bigint unsigned” [pk]

Default Value​

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 backticks: 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) [not null]
  source varchar(255) [default: 'direct']
  created_at timestamp [default: `now()`]
  rating integer [default: 10]
}

Index Definition​

Indexes allow users to quickly locate and access the data. Users can define single or multi-column indexes.

Table bookings {
  id integer
  country varchar
  booking_date date
  created_at timestamp

  indexes {
    (id, country) [pk] // composite primary key
    created_at [name: 'created_at_index', note: 'Date']
    booking_date
    (country, booking_date) [unique]
    booking_date [type: hash]
    (`id*2`)
    (`id*3`,`getdate()`)
    (`id*3`,id)
  }
}

There are 3 types of index definitions:

  • Index with single field (with index name): CREATE INDEX created_at_index on users (created_at)
  • Index with multiple fields (composite index): CREATE INDEX on users (created_at, country)
  • Index with an expression: CREATE INDEX ON films ( first_name + last_name )
  • (bonus) Composite index with expression: CREATE INDEX ON users ( country, (lower(name)) )

Index Settings​

  • type: type of index (btree, gin, gist, hash depending on DB). For now, only type btree and hash are accepted.
  • name: name of index
  • unique: unique index
  • pk: primary key

Relationships & Foreign Key Definitions​

Relationships are used to define foreign key constraints between tables across schemas.

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 4 types of relationships: one-to-one, one-to-many, many-to-one and many-to-many

  • <: 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
  • <>: many-to-many. E.g: authors.id <> books.id

In DBML, there are 3 syntaxes to define relationships:

// Long form
Ref name_optional {
  schema1.table1.column1 < schema2.table2.column2
}

// Short form:
Ref name_optional: schema1.table1.column1 < schema2.table2.column2

// Inline form
Table schema2.table2 {
  id integer
  column2 integer [ref: > schema1.table1.column1]
}

Note: if schema_name prefix is omitted, it'll default to public schema

Composite foreign keys:

Ref: merchant_periods.(merchant_id, country_code) > merchants.(id, country_code)

Cross-schema relationship:

Table core.users {
  id integer [pk]
}

Table blogging.posts {
  id integer [pk]
  user_id integer [ref: > core.users.id]
}

// or this
Ref: blogging.posts.user_id > core.users.id

Relationship settings​

Ref: products.merchant_id > merchants.id [delete: cascade, update: no action]
  • delete / update: cascade | restrict | set null | set default | no action Define referential actions. Similar to ON DELETE/UPDATE CASCADE/... in SQL.

Relationship settings are not supported for inline form ref.

Many-to-many relationship​

There're two ways to represent many-to-many relationship:

Beside presentation aspect, the main differece between these two approaches is how the relationship will be mapped into physical design when exporting to SQL.

Enum Definition​

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 belonged to default "public" schema
enum job_status {
  created [note: 'Waiting to be processed']
  running
  done
  failure
}

// enum belonged to a schema
enum v2.job_status {
  ...
}

Table jobs {
  id integer
  status job_status
  status_v2 v2.job_status
}

Note: if schema_name prefix is omitted, it'll default to public schema

If your enum values contain spaces or other special characters you can use double quotes.

enum grade {
  "A+"
  "A"
  "A-"
  "Not Yet Set"
}

Note Definition​

Note allows users to give description for a particular DBML element.

Table users {
  id int [pk]
  name varchar

  Note: 'This is a note of this table'
  // or
  Note {
  'This is a note of this table'
  }
}

Note's value is a string. If your note spans over multiple lines, you can use multi-line string to define your note.

Project Notes​

Project DBML {
  Note: '''
  # DBML - Database Markup Language
  DBML (database markup language) is a simple, readable DSL language designed to define database structures.

  ## Benefits

  * 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](http://dbdiagram.io)
  '''
}

Table Notes​

Table users {
  id int [pk]
  name varchar

  Note: 'Stores user data'
}

Column Notes​

You can add notes to your columns, so you can easily refer to it when hovering over the column 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
  ''']
}

TableGroup Notes​

TableGroup e_commerce [note: 'Contains tables that are related to e-commerce system'] {
  merchants
  countries

  // or
  Note: 'Contains tables that are related to e-commerce system'
}

Sticky Notes​

You can add sticky notes to the diagram canvas to serve as a quick reminder or to elaborate on a complex idea.

Example,

Table jobs {
  ...
}

Note single_line_note {
  'This is a single line note'
}

Note multiple_lines_note {
'''
  This is a multiple lines note
  This string can spans over multiple lines.
'''
}

TableGroup​

TableGroup allows users to group the related or associated tables together.

TableGroup tablegroup_name { // tablegroup is case-insensitive.
  table1
  table2
  table3
}

// example
TableGroup e_commerce1 {
  merchants
  countries
}

TableGroup Notes​

Table groupings can be annotated with notes that describe their meaning and purpose.

TableGroup e_commerce [note: 'Contains tables that are related to e-commerce system'] {
  merchants
  countries

  // or
  Note: 'Contains tables that are related to e-commerce system'
}

TableGroup Settings​

Each table group can take optional settings, defined within square brackets: [setting1: value1, setting2: value2, setting3, setting4]

The list of table group settings you can use:

  • note: 'string to add notes': add a note to this table group.
  • color: <color_code>: change the table group color.

Example,

TableGroup e_commerce [color: #345] {
  merchants
  countries
}

Multi-line String​

Multiline string will be defined between triple single quote '''

Note: '''
  This is a block string
  This string can spans over multiple lines.
'''
  • Line breaks: <enter> key
  • Line continuation: \ backslash
  • Escaping characters:
    • \: using double backslash \\
    • ': using \'
  • The number of spaces you use to indent a block string will be the minimum number of leading spaces among all lines. The parser will automatically remove the number of indentation spaces in the final output. The result of the above example will be:
  This is a block string
  This string can spans over multiple lines.

Comments​

Single-line Comments

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

Multi-line Comments

You can also put comment spanning multiple lines in your code by putting inside /* and */.

Example,

/*
  This is a
  Multi-lines
  comment
*/

Syntax Consistency​

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
  • triple quote as '''multi-line string''': multi-line string value
  • backtick `: function expression