Generated Types

Each column in a schema has a TypeScript type for type-safe select, insert, and update queries with Kysely.

Types for a schema can be retrieved using the infer method on the schema.

Consider the following table definition:

const users = table({
  columns: {
    id: integer().generatedAlwaysAsIdentity(),
    name: text(),
    createdAt: timestampWithTimeZone().default(sql`now()`).notNull(),
  },
  constraints: {
    primaryKey: primaryKey(["id"]),
  },
});

When we infer the types with:

type DB = typeof dbSchema.infer;

The DB type will be:

type DB = {
  users: {
    id: {
      readonly __select__: number;
      readonly __insert__: never;
      readonly __update__: never;
    };
    name: {
      readonly __select__: string;
      readonly __insert__: string | null | undefined;
      readonly __update__: string | null;
    },
    createdAt: {
      readonly __select__: Date;
      readonly __insert__: Date | undefined;
      readonly __update__: Date;
    },
  };
};

The types are inferred according to the column data types, constraints, default values and if the column is generated.

Column data types

Here's a table for select, insert, and update types for each column type:

Column	Select	Insert	Update
bigint	string	bigint | number | string	bigint | number | string
bigserial	string	bigint | number | string	bigint | number | string
bit	string	string	string
bitVarying	string	string	string
boolean	boolean	boolean | Boolish*	boolean | Boolish*
bytea	Buffer	Buffer | string	Buffer | string
characterVarying	string	string	string
character	string	string	string
cidr	string	string	string
date	Date	Date | string	Date | string
doublePrecision	string	bigint | number | string	bigint | number | string
enumerated	enum values	enum values	enum values
inet	string	string	string
integer	number	number | string	number | string
json	JsonValue*	JsonValue*	JsonValue*
jsonb	JsonValue*	JsonValue*	JsonValue*
macaddr	string	string	string
macaddr8	string	string	string
numeric	string	bigint | number | string	bigint | number | string
real	number	bigint | number | string	bigint | number | string
serial	number	number | string	number | string
smallint	number	number | string	number | string
time	string	string	string
timeWithTimeZone	string	string	string
timestamp	Date	Date | string	Date | string
timestampWithTimeZone	Date	Date | string	Date | string
tsquery	string	string	string
tsvector	string	string	string
uuid	string	string	string
xml	string	string	string

(*) Boolish and JsonValue are defined as follows:

type Boolish = "true" | "false" | "yes" | "no" | 1 | 0 | "1" | "0" | "on" | "off";
type JsonArray = JsonValue[];
type JsonValue = boolean | number | string | Record<string, unknown> | JsonArray;

Optionality and nullability

By default, columns have:

• Nullable selects, inserts and updates.
• Optional inserts and updates.

Columns will have their optionality and nullability changed accordingly to the constraints they have, their default data value, and if they are generated:

Column	Optional	Nullable
with default data value	yes	yes
with NOT NULL constraint	no	no
with NOT NULL constraint with default data value	yes	no
serial	yes	no
bigserial	yes	no
generated by default as identity	yes	no
primary key	no	no
serial, bigserial generated by default as identity primary key	yes	no

Examples

Type of an integer column named id:

type id = {
  readonly __select__: number | null;
  readonly __insert__: number | string | null | undefined;
  readonly __update__: number | string | null;
};

Generated always as identity will not accept inserts or updates:

type id = {
  readonly __select__: number;
  readonly __insert__: never;
  readonly __update__: never;
};

Type of an integer column with a NOT NULL constraint:

type id = {
  readonly __select__: number;
  readonly __insert__: number | string;
  readonly __update__: number | string;
};

Type of an integer column with a default data value and a NOT NULL constraint:

type id = {
  readonly __select__: number;
  readonly __insert__: number | string | undefined;
  readonly __update__: number | string;
};

Type of an bigint column generated by default as identity:

type id = {
  readonly __select__: string;
  readonly __insert__: bigint | number | string | undefined;
  readonly __update__: bigint | number | string;
};