---

name: bknd-add-field description: Use when adding a field to an existing Bknd entity. Covers all field types (text, number, boolean, date, enum, json, jsonschema, media), field modifiers (.required(), .unique(), .default()), validation options, and UI vs code approaches.

Add Field to Entity

Add a new field (column) to an existing entity in Bknd.

Prerequisites

• Existing Bknd entity (see bknd-create-entity)
• For code mode: Access to your schema file

When to Use UI vs Code

Use UI Mode When

• Quick iteration/prototyping
• Non-developer adding fields
• Testing field configurations before coding

Use Code Mode When

• Version control needed
• Reproducible schema changes
• Type safety required
• Team collaboration

UI Approach

Step 1: Access Entity

1. Start server: npx bknd run
2. Open http://localhost:1337
3. Navigate to Data section
4. Click on the target entity (e.g., posts)

Step 2: Add Field

1. Click + Add Field
2. Select field type from dropdown:
   • Text: Strings, emails, URLs
   • Number: Integers, decimals
   • Boolean: True/false
   • Date: Timestamps
   • Enum: Fixed set of values
   • JSON: Unstructured data
3. Enter field name (snake_case: first_name, created_at)

Step 3: Configure Options

Based on field type, configure:

All Types:

• Required: Toggle on if field cannot be null
• Default Value: Set a default

Text:

• Min/Max Length
• Pattern (regex validation)

Number:

• Minimum/Maximum values
• Multiple Of (for integers)

Enum:

• Add enum values (one per line)

Step 4: Save and Sync

1. Click Save Field
2. Click Sync Database to apply changes

Code Approach

Step 1: Locate Entity Definition

Find your entity in the schema:

Copyconst schema = em({
  posts: entity("posts", {
    title: text().required(),
    // Add new fields here
  }),
});

Step 2: Add Field

Add the new field to the entity's field object:

Copyconst schema = em({
  posts: entity("posts", {
    title: text().required(),
    subtitle: text(),           // NEW: optional text field
    view_count: number(),       // NEW: optional number field
  }),
});

Step 3: Restart Server

Bknd auto-syncs schema on startup. Restart your server to apply changes.

Field Types Reference

Text Field

Copyimport { text } from "bknd";

entity("users", {
  // Basic optional text
  bio: text(),

  // Required text
  email: text().required(),

  // Unique constraint
  username: text().unique(),

  // With validation
  slug: text({
    minLength: 3,
    maxLength: 100,
    pattern: "^[a-z0-9-]+$",
  }).required(),

  // With default value
  status: text({ default_value: "active" }),
})

Number Field

Copyimport { number } from "bknd";

entity("products", {
  // Basic number
  quantity: number(),

  // Required with validation
  price: number({
    minimum: 0,
    maximum: 99999.99,
  }).required(),

  // Integer only (multipleOf: 1)
  rating: number({
    minimum: 1,
    maximum: 5,
    multipleOf: 1,
  }),
})

Boolean Field

Copyimport { boolean } from "bknd";

entity("posts", {
  // Defaults to false
  published: boolean(),

  // Default true
  active: boolean({ default_value: true }),
})

Date Field

Copyimport { date } from "bknd";

entity("events", {
  // Basic date
  start_date: date().required(),

  // Auto-set to current time
  created_at: date({ default_value: "now" }),
})

Enum Field

Note: Import is enumm (double 'm') to avoid JS reserved word.

Copyimport { enumm } from "bknd";

entity("posts", {
  // Array syntax
  status: enumm({
    enum: ["draft", "published", "archived"],
    default_value: "draft",
  }).required(),

  // Object syntax (key-value)
  priority: enumm({
    enum: {
      LOW: "low",
      MEDIUM: "medium",
      HIGH: "high",
    },
    default_value: "MEDIUM",
  }),
})

JSON Field

Copyimport { json } from "bknd";

entity("users", {
  // Untyped JSON
  metadata: json(),

  // Typed JSON (TypeScript only, no runtime validation)
  preferences: json<{
    theme: "light" | "dark";
    notifications: boolean;
  }>(),

  // With default
  tags: json<string[]>({ default_value: [] }),
})

JSON Schema Field

For runtime-validated JSON:

Copyimport { jsonschema } from "bknd";

entity("webhooks", {
  payload: jsonschema({
    type: "object",
    properties: {
      event: { type: "string" },
      timestamp: { type: "number" },
    },
    required: ["event", "timestamp"],
  }),
})

Media Field

For file attachments:

Copyimport { media } from "bknd";

entity("posts", {
  // Single file
  cover_image: media({ entity: "posts" }),

  // Multiple files with constraints
  gallery: media({
    entity: "posts",
    min_items: 1,
    max_items: 10,
    mime_types: ["image/jpeg", "image/png", "image/webp"],
  }),
})

Field Modifiers

Chain modifiers after field type:

Chaining example:

Copyentity("users", {
  email: text().required().unique(),
  role: text().default("user"),
  org_id: number().references("organizations.id"),
})

Field Naming Conventions

Common Pitfalls

Field Already Exists

Error: Field "title" already exists on entity "posts"

Fix: Each field name must be unique within an entity. Choose a different name.

Invalid Field Name

Error: Invalid field name

Fix: Use lowercase letters, numbers, and underscores. Must start with letter.

Copy// Valid
title: text()
first_name: text()
item_2: text()

// Invalid
Title: text()        // No uppercase
2_item: text()       // Can't start with number
first-name: text()   // No hyphens

Enum Import Mistake

Error: enum is a reserved word

Fix: Import and use enumm (double 'm'):

Copy// Wrong
import { enum } from "bknd";

// Correct
import { enumm } from "bknd";

status: enumm({ enum: ["a", "b"] })

Missing Required Modifier on Existing Data

Problem: Adding .required() to field on entity with existing null values.

Fix: Either:

1. Update existing records to have non-null values first
2. Add a default value: text({ default_value: "N/A" }).required()
3. Keep field optional

Field Changes Not Reflecting

Problem: Added field in code but not appearing.

Fixes:

1. Restart the server (schema syncs on startup)
2. Verify field is in the correct entity definition
3. Check for syntax errors in schema

Verification

UI Mode

1. Click on entity in Data section
2. Verify new field appears in field list
3. Create a test record with the new field

Code Mode

Copyconst api = app.getApi();

// Create record with new field
const result = await api.data.createOne("posts", {
  title: "Test",
  subtitle: "New field test",  // Your new field
});
console.log(result);

CLI Check

Copynpx bknd debug paths
# Check entity fields in output

DOs and DON'Ts

DO:

• Use snake_case for field names
• Start with optional fields; make required later if needed
• Add default values for required fields on existing data
• Use appropriate field types (don't store numbers as text)

DON'T:

• Use enum import (use enumm)
• Add .required() to existing entities without defaults
• Use camelCase or PascalCase for field names
• Create redundant fields (e.g., id is auto-generated)

Related Skills

• bknd-create-entity - Create a new entity first
• bknd-define-relationship - Add relationships between entities
• bknd-modify-schema - Rename or change field types
• bknd-crud-create - Insert data using new fields