`DEFINE FIELD` statement

The DEFINE FIELD statement allows you to instantiate a named field on a table, enabling you to set the field's data type, set a default value, apply assertions to protect data consistency, and set permissions specifying what operations can be performed on the field.

Requirements

You must be authenticated as a root owner or editor, namespace owner or editor, or database owner or editor before you can use the DEFINE FIELD statement.
You must select your namespace and database before you can use the DEFINE FIELD statement.

Statement syntax

Regular fields

SurrealQL Syntax

DEFINE FIELD [ OVERWRITE | IF NOT EXISTS ] @name ON [ TABLE ] @table
	[ TYPE @type | object [ FLEXIBLE ] ]
	[ REFERENCE 
		[ ON DELETE REJECT | 
			ON DELETE CASCADE | 
			ON DELETE IGNORE |
			ON DELETE UNSET | 
			ON DELETE THEN @expression ]
	]
	[ DEFAULT [ALWAYS] @expression ]
  [ READONLY ]
	[ VALUE @expression ]
	[ ASSERT @expression ]
	[ PERMISSIONS [ NONE | FULL
		| FOR select @expression
		| FOR create @expression
		| FOR update @expression
	] ]
  [ COMMENT @string ]

Computed fields

Note

In versions of SurrealDB before 3.0.0-beta, COMPUTED fields were implemented using a data type called a future. Please see the page on futures in this case.

A COMPUTED field is one that is not stored but computed every time it is accessed. Such fields have a more limited set of clauses that can be used. Furthermore, a COMPUTED field cannot be defined on the id field of a record, nor any nested fields (i.e. a field metadata can be defined as computed, but not medatata.can_drive).

SurrealQL Syntax

DEFINE FIELD [ OVERWRITE | IF NOT EXISTS ] @name ON [ TABLE ] @table
	COMPUTED @expression
	[ TYPE @type | object [ FLEXIBLE] ]
	[ PERMISSIONS [ NONE | FULL
		| FOR select @expression
		| FOR create @expression
		| FOR update @expression
	] ]
  [ COMMENT @string ]

Example usage

The following expression shows the simplest way to use the DEFINE FIELD statement.

-- Declare the name of a field.
DEFINE FIELD email ON TABLE user;

The fields of an object and the items in an array can be defined individually using the . operator for objects, or the indexing operator for arrays.

-- Define nested object property types
DEFINE FIELD emails.address ON TABLE user TYPE string;
DEFINE FIELD emails.primary ON TABLE user TYPE bool;

-- Define individual fields on an array
DEFINE FIELD metadata[0] ON person TYPE datetime;
DEFINE FIELD metadata[1] ON person TYPE int;

Defining data types

The DEFINE FIELD statement allows you to set the data type of a field. For a full list of supported data types, see Data types.

From version v2.2.0, when defining nested fields, where both the parent and the nested fields have types defined, it is no longer possible to have mismatching types, to prevent any impossible type issues once the schema is defined.

For example, the following will fail:

DEFINE FIELD OVERWRITE fd ON c TYPE { a: string, b: number };
DEFINE FIELD OVERWRITE fd.* ON c TYPE number;

The above will fail with the following error:

'Cannot set field `fd.*` with type `number` as it mismatched with field `fd` with type `{ a: string, b: number }`'

Simple data types

-- Set a field to have the string data type
DEFINE FIELD email ON TABLE user TYPE string;

-- Set a field to have the datetime data type
DEFINE FIELD created ON TABLE user TYPE datetime;

-- Set a field to have the bool data type
DEFINE FIELD locked ON TABLE user TYPE bool;

-- Set a field to have the number data type
DEFINE FIELD login_attempts ON TABLE user TYPE number;

A | vertical bar can be used to allow a field to be one of a set of types. The following example shows a field that can be a UUID or an int, perhaps for user records that have varying data due to two diffent legacy ID types.

-- Set a field to have either the uuid or int type
DEFINE FIELD user_id ON TABLE user TYPE uuid|int;

Array type

You can also set a field to have the array data type. The array data type can be used to store a list of values. You can also set the data type of the array's contents, as well as the required number of items that it must hold.

-- Set a field to have the array data type
DEFINE FIELD roles ON TABLE user TYPE array<string>;

-- Set a field to have the array data type, equivalent to `array<any>`
DEFINE FIELD posts ON TABLE user TYPE array;

-- Set a field to have the array object data type
DEFINE FIELD emails ON TABLE user TYPE array<object>;

-- Set a field that holds exactly 640 bytes
DEFINE FIELD bytes ON TABLE data TYPE array<int, 640> ASSERT $value.all(|$val| $val IN 0..=255);

-- Field for a block in a game showing the possible distinct directions a character can move next.
-- The array can contain no more than four directions
DEFINE FIELD next_paths ON TABLE block 
  TYPE array<"north" | "east" | "south" | "west"> 
  VALUE $value.distinct() 
  ASSERT $value.len() <= 4;

Making a field optional

You can make a field optional by wrapping the inner type in an option, which allows you to store NONE values in the field.

-- A user may enter a biography, but it is not required.
-- By using the option type you also allow for NONE values.
DEFINE FIELD biography ON TABLE user TYPE option<string>;

The example below shows how to define a field user on a POST table. The field is of type record. This means that the field can store a record<user> or NONE.

DEFINE FIELD user ON TABLE post TYPE option<record<user>>;

Flexible data types

Flexible types allow you to have SCHEMALESS functionality on a SCHEMAFULL table. This is necessary for working with nested object types that need to be able to accept fields that have not yet been defined.

DEFINE TABLE user SCHEMAFULL;
DEFINE FIELD name ON TABLE user TYPE string;
DEFINE FIELD metadata ON TABLE user FLEXIBLE TYPE object;
DEFINE FIELD metadata.user_id ON TABLE user TYPE int;
DEFINE FIELD name ON user TYPE string;
DEFINE FIELD metadata ON TABLE user TYPE object FLEXIBLE;
DEFINE FIELD metadata.user_id ON TABLE user TYPE int;

Taking the following CREATE statement:

CREATE ONLY user SET
  name = "User1",
  metadata = {
      user_id: 8876687,
      country_code: "ee",
      time_zone: "EEST",
      age: 25
};

Without FLEXIBLE, the metadata field will effectively be a SCHEMAFULL object with only a single defined field.

In versions of SurrealDB before 3.0, the result of the above statement was a record in which the metadata field was only able to populate the user_id field.

{
	id: user:ke8w4u38gbm3ofp2u8fb,
	metadata: {
		user_id: 8876687
	},
  name: "User1"
}

As of version 3.0, the statement now returns an error upon finding the first field that was not defined in the schema.

"Found field 'metadata.age', but no such field exists for table 'user'"

With FLEXIBLE, the output will be as expected as the schema now allows any sort of object to be a field on the user table — as long as values for name and metadata.user_id are present.

Response

{
	id: user:lsdk473e279oik1k484b,
	metadata: {
		age: 25,
		country_code: 'ee',
		time_zone: 'EEST',
		user_id: 8876687
	},
	name: 'User1'
}

Using the `DEFAULT` clause to set a default value

You can set a default value for a field using the DEFAULT clause. The default value will be used if no value is provided for the field.

-- A user is not locked by default.
DEFINE FIELD locked ON TABLE user TYPE bool
-- Set a default value if empty
  DEFAULT false;

Using the `DEFAULT` and `ALWAYS` clause

In addition to the DEFAULT clause, you can use the DEFAULT ALWAYS clause to set a default value for a field. The ALWAYS keyword indicates that the DEFAULT clause is used not only on CREATE, but also on UPDATE if the value is empty (NONE).

DEFINE TABLE product SCHEMAFULL;
-- Set a default value of 123.456 for the primary field
DEFINE FIELD primary ON product TYPE number DEFAULT ALWAYS 123.456;

With the above definition, the primary field will be set to 123.456 when a new product is created without a value for the primary field or with a value of NONE, and when an existing product is updated if the value is specified the result will be the new value.

In the case of NULL or a mismatching type, an error will be returned.

-- This will return an error
CREATE product:test SET primary = NULL;

-- result 
"Couldn't coerce value for field `primary` of `product:test`: Expected `number` but found `NULL`"

On the other hand, if a valid number is provided during creation or update, that number will be used instead of the default value. In this case, 123.456.

-- This will set the value of the `primary` field to `123.456`
CREATE product:test;

-- This will set the value of the `primary` field to `463.456`
UPSERT product:test SET primary = 463.456;

-- This will set the value of the `primary` field to `123.456`
UPSERT product:test SET primary = NONE;

Query

DEFINE TABLE post SCHEMAFULL;
DEFINE FIELD tags ON post TYPE array<object> DEFAULT ALWAYS [];
DEFINE FIELD tags.*.color ON post TYPE string DEFAULT ALWAYS 'red';
DEFINE FIELD tags.*.name ON post TYPE string;
--
CREATE post:test;
UPSERT post:test SET tags += { name: 'test' };
UPSERT post:test SET tags += { name: 'test', color: 'blue' };

Response

[{ id: post:test, tags: [] }]

[{ id: post:test, tags: [{ color: 'red', name: 'test' }] }]

[{ id: post:test, tags: [{ color: 'red', name: 'test' }, { color: 'blue', name: 'test' }] }]

Using the `VALUE` clause to set a field's value

The VALUE clause differs from DEFAULT in that a default value is calculated if no other is indicated, otherwise accepting the value given in a query.

DEFINE FIELD updated ON TABLE user DEFAULT time::now();

-- Set `updated` to the year 1900
CREATE user SET updated = d"1900-01-01";
-- Then set to the year 1910
UPDATE user SET updated = d"1910-01-01";

A VALUE clause, on the other hand, will ignore attempts to set the field to any other value.

DEFINE FIELD updated ON TABLE user VALUE time::now();

-- Ignores 1900 date, sets `updated` to current time
CREATE user SET updated = d"1900-01-01";
-- Ignores again, updates to current time
UPDATE user SET updated = d"1900-01-01";

As the example above shows, a VALUE clause sets the value every time a record is modified (created or updated). However, the value will not be recalculated in a SELECT statement, which simply accesses the current set value.

DEFINE FIELD updated ON TABLE user VALUE time::now();

CREATE user:one;
SELECT * FROM ONLY user:one;
-- Sleep for one second
SLEEP 1s;
-- `updated` is still the same
SELECT * FROM ONLY user:one;

To create a field that is calculated each time it is accessed, a computed field can be used.

DEFINE FIELD accessed_at ON TABLE user COMPUTED time::now();

CREATE user:one;
SELECT * FROM ONLY user:one;
-- Sleep for one second
SLEEP 1s;
-- `accessed_at` is a different value now
SELECT * FROM ONLY user:one;

Altering a passed value

You can alter a passed value using the VALUE clause. This is useful for altering the value of a field before it is stored in the database.

In the example below, the VALUE clause is used to ensure that the email address is always stored in lowercase characters by using the string::lowercase function.

-- Ensure that an email address is always stored in lowercase characters
DEFINE FIELD email ON TABLE user TYPE string
  VALUE string::lowercase($value);

Asserting rules on fields

You can take your field definitions even further by using asserts. Assert can be used to ensure that your data remains consistent. For example you can use asserts to ensure that a field is always a valid email address, or that a number is always positive.

-- Give the user table an email field. Store it in a string
DEFINE FIELD email ON TABLE user TYPE string
  -- Check if the value is a properly formatted email address
  ASSERT string::is_email($value);

As the ASSERT clause expects an expression that returns a boolean, an assertion with a custom message can be manually created by returning true in one case and using a THROW clause otherwise.

DEFINE FIELD num ON data TYPE int ASSERT {
    IF $input % 2 = 0 {
        RETURN true
    } ELSE {
        THROW "Tried to make a " + <string>$this + " but `num` field requires an even number"
    }
};

CREATE data:one SET num = 11;

Error output

'An error occurred: Tried to make a { id: data:one, num: 11 } but `num` field requires an even number'

Making a field `READONLY`

The READONLY clause can be used to prevent any updates to a field. This is useful for fields that are automatically updated by the system. To make a field READONLY, add the READONLY clause to the DEFINE FIELD statement. As seen in the example below, the created field is set to READONLY.

DEFINE FIELD created ON resource VALUE time::now() READONLY;

Using `IF NOT EXISTS` clause

The IF NOT EXISTS clause can be used to define a field only if it does not already exist. You should use the IF NOT EXISTS clause when defining a field in SurrealDB if you want to ensure that the field is only created if it does not already exist. If the field already exists, the DEFINE FIELD statement will return an error.

It's particularly useful when you want to safely attempt to define a field without manually checking its existence first.

On the other hand, you should not use the IF NOT EXISTS clause when you want to ensure that the field definition is updated regardless of whether it already exists. In such cases, you might prefer using the OVERWRITE clause, which allows you to define a field and overwrite an existing one if it already exists, ensuring that the latest version of the definition is always in use

-- Create a field if it does not already exist
DEFINE FIELD IF NOT EXISTS email ON TABLE user TYPE string;

Using `OVERWRITE` clause

The OVERWRITE clause can be used to define a field and overwrite an existing one if it already exists. You should use the OVERWRITE clause when you want to modify an existing field definition. If the field already exists, the DEFINE FIELD statement will overwrite the existing definition with the new one.

-- Overwrite the current field definition if it already exists
DEFINE FIELD OVERWRITE example ON TABLE user TYPE string;

Setting permissions on fields

By default, the permissions on a field will be set to FULL unless otherwise specified.

DEFINE FIELD some_info ON TABLE some_table TYPE string;
INFO FOR TABLE some_table;

Response

{
	events: {},
	fields: {
		info: 'DEFINE FIELD info ON some_table TYPE string PERMISSIONS FULL'
	},
	indexes: {},
	lives: {},
	tables: {}
}

You can set permissions on fields to control who can perform operations on them using the PERMISSIONS clause. The PERMISSIONS clause can be used to set permissions for SELECT, CREATE, and UPDATE operations. The DELETE operation only relates to records and, as such, is not available for fields.

-- Set permissions for the email field
DEFINE FIELD email ON TABLE user
  PERMISSIONS
    FOR select WHERE published=true OR user=$auth.id
    FOR update WHERE user=$auth.id OR $auth.role="admin";

Array with allowed values

By using an Access Control List as an example we can show how we can restrict what values can be stored in an array. In this example we are using an array to store the permissions for a user on a resource. The permissions are restricted to a specific set of values.

-- An ACL can be applied to any kind of resource (record)
DEFINE FIELD resource ON TABLE acl TYPE record;
-- We associate the acl with a user using record<user>
DEFINE FIELD user ON TABLE acl TYPE record<user>;

-- The permissions for the user+resource will be stored in an array.
DEFINE FIELD permissions ON TABLE acl TYPE array
  -- The array must not be empty because at least one permission is required to make a valid ACL
  -- The items in the array must also be restricted to specific permissions
  ASSERT
      array::len($value) > 0
      AND $value ALLINSIDE ["create", "read", "write", "delete"];

-- SEE IT IN ACTION
-- 1: Add users
CREATE user:tobie SET firstName = 'Tobie', lastName = 'Hitchcock',
  email = 'Tobie.Hitchcock@surrealdb.com';
CREATE user:abc SET firstName = 'A', lastName = 'B',
  email = 'c@d.com';
CREATE user:efg SET firstName = 'E', lastName = 'F',
  email = 'g@h.com';

-- 2: Create a resource
CREATE document:SurrealDB_whitepaper SET
  name = "some messaging queue";

-- 3: Associate with ACL
CREATE acl SET user = user:tobie, resource = document:SurrealDB_whitepaper, permissions = ["create", "write", "read"];
CREATE acl SET user = user:abc, resource = document:SurrealDB_whitepaper, permissions = ["read", "delete"];

-- Test Asserts using failure examples
-- A: Create ACL without permissions field
CREATE acl:invalid SET
  user = user:efg,
  permissions = [], # FAIL - permissions must not be empty
  resource = document:SurrealDB_whitepaper;
-- B: Create acl with invalid permisson
CREATE acl:also_invalid SET
  user = user:efg,
  permissions = ["all"], # FAIL - This value is not allowed in the array
  resource = document:SurrealDB_whitepaper;

Using RegEX to validate a string

You can use the ASSERT clause to apply a regular expression to a field to ensure that it matches a specific pattern. In the example below, the ASSERT clause is used to ensure that the countrycode field is always a valid ISO-3166 country code.

-- Specify a field on the user table
DEFINE FIELD countrycode ON user TYPE string
	-- Ensure country code is ISO-3166
	ASSERT $value = /[A-Z]{3}/
	-- Set a default value if empty
	VALUE $value OR $before OR 'GBR'
;

Interacting with other fields of the same record

While a DEFINE TABLE statement represents a template for any subsequent records to be created, a DEFINE FIELD statement pertains to concrete field data of a record. As such, a DEFINE FIELD statement gives access to the record's other fields through their names, as well as the current field through the $value parameter.

DEFINE TABLE person SCHEMAFULL;

DEFINE FIELD first_name ON TABLE person TYPE string VALUE string::lowercase($value);
DEFINE FIELD last_name  ON TABLE person TYPE string VALUE string::lowercase($value);
DEFINE FIELD name       ON TABLE person             VALUE first_name + ' ' + last_name;

// Creates a `person` with the name "bob bobson"
CREATE person SET first_name = "BOB", last_name = "BOBSON";

The $this parameter gives access to the entire record on which a field is defined.

DEFINE FIELD extra_self ON TABLE person VALUE $this;
CREATE person:one SET name = "Little person", age = 6;

Output

[
	{
		age: 6,
		extra_self: {
			age: 6,
			id: person:one,
			name: 'Little person'
		},
		id: person:one,
		name: 'Little person'
	}
]

Order of operations when setting a field's value

As DEFINE FIELD statements are computed in alphabetical order, be sure to keep this in mind when using fields that rely on the values of others.

The following example is identical to the above except that full_name has been chosen for the previous field name. The full_name field will be calculated after first_name, but before last_name.

DEFINE TABLE person SCHEMAFULL;

DEFINE FIELD first_name ON TABLE person TYPE string VALUE string::lowercase($value);
DEFINE FIELD last_name  ON TABLE person TYPE string VALUE string::lowercase($value);
DEFINE FIELD full_name  ON TABLE person             VALUE first_name + ' ' + last_name;

// Creates a `person` with `full_name` of "bob BOBSON", not "bob bobson"
CREATE person SET first_name = "Bob", last_name = "BOBSON";

A good rule of thumb is to organize your DEFINE FIELD statements in alphabetical order so that the field definitions show up in the same order as that in which they are computed.

Defining a literal on a field

A field can also be defined as a literal type, by specifying one or more possible values and/or permitted types.

DEFINE FIELD coffee ON TABLE order TYPE "regular" | "large" | { special_order: string };

CREATE order:good SET coffee = { special_order: "Venti Quadruple Ristretto Half-Decaf Soy Latte with 4 pumps of sugar-free vanilla syrup" };
CREATE order:bad SET coffee = "small";

Response

-------- Query --------

[
	{
		coffee: {
			special_order: 'Venti Quadruple Ristretto Half-Decaf Soy Latte with 4 pumps of sugar-free vanilla syrup'
		},
		id: order:good
	}
]

-------- Query --------
"Found 'small' for field `coffee`, with record `order:bad`, but expected a 'regular' | 'large' | { special_order: string }"

One more example of a literal containing settings for a full text search filter:

DEFINE FIELD filter ON TABLE search_settings TYPE
      "None"
    | { type: "Ascii" }
    | { type: "EdgeNgram", from: int, to: int }
    | { type: "Lowercase" }
    | { type: "Ngram", from: int, to: int }
    | { type: "Snowball", language: string }
    | { type: "Uppercase" };

Defining a `TYPE` for the `id` field

The DEFINE FIELD statement can be defined for the id field to specify the acceptable type of ID.

DEFINE FIELD id ON TABLE something TYPE string;
DEFINE FIELD id ON TABLE something TYPE int;
DEFINE FIELD id ON TABLE something TYPE uuid;

Complex IDs can be specified as well.

-- using multiple data types for a Complex Record ID
DEFINE FIELD id ON TABLE log TYPE [record, "info" | "warn" | "error", datetime];

-- Incorrect ID format, generates an error
CREATE log:bad SET level = "info", time = time::now(), message = "Database started";

-- Acceptable ID format
CREATE log:[user:one, "info", time::now()] SET message = "Database started";

Output

-------- Query --------

"Couldn't coerce value for field `id` of `log:bad`: Expected `[record, 'info' | 'warn' | 'error', datetime]` but found `'bad'`"

-------- Query --------

[
	{
		id: log:[
			user:one,
			'info',
			d'2025-03-25T03:36:16.323Z'
		],
		message: 'Database started'
	}
]

Defining a reference

A field that is a record link (type record, option<record>, array<record<person>>, and so on) can be defined as a REFERENCE. If this clause is used, any linked to record will be able to define a field of its own of type references which will be aware of the incoming links.

For more information, see the page in the datamodel section on references.

DEFINE FIELD statement

Requirements

Statement syntax

Regular fields

Computed fields

Note

Example usage

Defining data types

Simple data types

Array type

Making a field optional

Flexible data types

Using the DEFAULT clause to set a default value

Using the DEFAULT and ALWAYS clause

Using the VALUE clause to set a field's value

Altering a passed value

Asserting rules on fields

Making a field READONLY

Using IF NOT EXISTS clause

Using OVERWRITE clause

Setting permissions on fields

Array with allowed values

Using RegEX to validate a string

Interacting with other fields of the same record

Order of operations when setting a field's value

Defining a literal on a field

Defining a TYPE for the id field

Defining a reference

`DEFINE FIELD` statement

Using the `DEFAULT` clause to set a default value

Using the `DEFAULT` and `ALWAYS` clause

Using the `VALUE` clause to set a field's value

Making a field `READONLY`

Using `IF NOT EXISTS` clause

Using `OVERWRITE` clause

Defining a `TYPE` for the `id` field