How Knack Works
Design Your Database
Manage Your Records
Build Your Live Application
View and Share Your App
Do More With Knack
Connect Related Data
Users & Access
Calculations & Logic
Emails & Notifications
Search & Queries
Reporting & Dashboards
E-Commerce & Payments
Tables & Connections
Plan Your Connections: Complex Example
Working With Tables
Plan Your Connections: Simple Example
Plan Your Tables
Use Connections in Your App
Connecting Records Together
Connections: Troubleshooting & FAQs
Numeric Equation Functions
Date Equation Settings
Numeric Equation Settings
Text Formula Functions
CSV Format Guide for Importing
Working with Records
Deleting a Page That's Being Linked to
Working with Pages
Navigating the Page Preview
Printing Pages & PDFs
Grid Column Settings
Source: Which Records Will the View Display
Using Action Links
Combining Fields from Connected Records in Views
Using Record Rules
Using Display Rules
Using Submit Rules
Users & Logins
Users and the Page Menu
Manage Roles & Permissions
Single Sign-On with Google, Facebook, Twitter, and Custom
Manage User Records
Logins and Registrations
Live App Security Settings: HIPAA Plans
Live App Security Settings
Tasks & Emails
How do I cancel my Knack account?
I'm over the storage limit for my account. How do I add more storage or get under the limit?
Need account access or to transfer account access because account owner or colleague left the company
I'm over the record limit for my account. How do I add more records or get under the limit?
Is there an option to pay via invoice, check, wire transfer, or something other than a credit card?
How do I freeze or pause my Knack account?
Where can I find a copy of my receipt or invoice?
How do I add more API calls to my account?
How do I change the favicon for my app?
How do I backup or export my apps and data?
How can I track what users are doing in my app?
How do I remove the "Powered by Knack" logo at the bottom of my app?
How do I give Builder access to a colleague or developer for one of my apps?
How do I white label my app?
How do I copy an app from my account to another account?
How do I show multiple dates on a calendar?
How do I add a logo to my app?
How do I find the most recent date from a connected table?
How do I create a field that always shows today's date?
Can I share or connect data between apps?
How do I create an "If, Then" or conditional equation?
How do I merge my apps, or copy pages, tables, or other app elements between my apps?
The menu isn't showing for my app on mobile devices. How do I fix that?
Is there a way to have new users be automatically logged-in after they register?
How do I bulk upload or import multiple files?
How do I move or copy fields or data from one table to another?
How can I show a customer's payment history if I'm collecting payments through my Knack app and through cash or check?
Is there a way to add a display rule to multiple columns at one time instead of having to update each column individually?
Do I need a separate user role table for my Vendors, Customers, Employees, Contacts, etc.?
How can I set up my app so users see only their own data?
Can I combine two date fields into a single date field? For example, combining a start and end date into a single field?
Does Knack offer a service for building apps or have developers I can hire?
How do I bulk upload or import multiple images?
How can I change the color of something in my app?
Is it possible to display more than 100 records at a time on a grid, list, or search view?
Can I migrate or transfer data from Zoho, Quickbase, or TrackVia?
Can I add chat or messaging to my app?
Can I sell my Knack apps?
Can I use Knack on mobile devices?
Do you have a sandbox or developer environment?
Can I send SMS or text messages using Knack?
Can I integrate Knack with other data, products, and services?
Can I create invoices and accept payments?
Can I have an app in a language besides English?
Can I email PDFs or other attachments to users with Knack?
Can I add Google Analytics to my Knack app?
Can I migrate my Access, Filemaker, SQL, or other databases?
Can I prototype for others?
Can I customize the look and feel of my Knack pages?
Can I use a barcode or credit card scanner with Knack?
How secure is Knack?
Does the signature captured through a signature field constitute a legally binding signature?
Does Knack offer a partner program?
How does Knack work on mobile devices? Is it mobile-friendly? Can users download my apps?
Is Knack GDPR compliant?
Storing sensitive data (credit cards, social security numbers, etc.)
Will Knack sign an NDA (Non-Disclosure Agreement)?
Which browsers do you support?
How do I batch download all of the images and files In my app?
I'm seeing an odd character when importing data. How can I get rid of it?
How do I update existing data using an import?
My import is failing or getting stuck. What do I do?
Can I undo or reverse an import?
I'm having trouble importing into a specific type of field. What can I do?
Some of my fields aren't importing correctly. How can I fix that?
I'm having trouble importing into a connection field. What can I do?
Can I import something other than data? Like tables, pages, views, etc?
My import is taking a long time. Can you take a look?
I'm getting an error when importing. What do I do?
Do the validation rules on fields trigger when importing data?
Can I schedule or automate imports?
Can my users import data from the live app, instead of going through the builder/back-end?
I am importing data for the first time. How do I do that?
Can I import data into more than one table at the same time?
How To Guides
Add Functionality to Your Live App
How To Create Discount Codes
Create an Add To Favorites Feature
How to Access Private Records Without a Login
Accept Payments in a Live App
Manage Your Records
Use an Edit Form to Create Records If They Don't Exist
Track Which User Last Updated a Record
Copy a Record Using Record Rules
Track When Records are Created and Updated
Create a Version History for Records
Use Zapier to Insert Connected Records
Work with Connected Records
How to Show Multiple Fields in Your Connection Drop-Down
Showing Parent-Child Records in the Live App
How to Create Dynamic Dropdowns in Forms
Add Read-Only Fields to a Form
How to Change the Layout of Forms
Create a Multi-Part Form
How to Allow Users to Add New Options in Forms
How to Add Instructions to a Form
How to Customize the Text on a Submit Button
How to Automatically Capture a User’s Location on a Form
How to Use URL Variables to Pre-Populate a Form
How to Add a Map to a Details View
How to Add Connection Links to Views
How to Add Inline Editing to a Grid
Create a Print-Friendly Invoice Page
How to Click on an Image to Go to Another Page
How to Add Groupings to a Grid
Users & Logins
Force Users to Reset Their Passwords
Save a User's Payment Method
Create a Single Login Page for Multiple User Roles
Add Read-Only Access For Users
Show Records Connected To The Logged-in User's Company Or Other Group
Show Records Connected to the Logged-in User
Create an Admin User Role to View All Records
Workflow & Automations
Add a Pipeline to Your App
Create a Registration Form with Limited Availability
Add Stages to Your App
Store Multiple Images or Files for Individual Records
Use Multiple Image Sources for a Single Image Field
Create a Button or Link that Updates a Field to a Custom Value
Notify a User That an Item is Ready for Review
Add Assignments to Your App
Approve New Records Before Displaying Them
Add Notification & Reminder Emails to Your App
Add Status Indicators to Your App
Logic, Equations & Formulas
Start an Auto Increment Field from Any Number
Display a Message When a Deadline is Approaching
Generate Simple Numeric Barcodes Automatically
How to Set a Random ID
Calculate Age in Years from a Birthday
How To Number Line Items
Show Upcoming Birthdays
How to Extract the Start and End Dates from a Date/Time Field
How to Display Multiple Date Formats Using a Single Date Field
Reports, Queries, and Summaries
Build an Inventory Manager App
Build a Quiz App
Build a Warehouse Manager App
Build a Member Directory
Build an Orders App
Build a Map Directory or Store Locator App
Images & Files
Manage Your Account
Manage Your Account
About Knack Accounts
Account Plans and Billing
Managing Your Apps
Managing Your Account Settings
Sharing Apps With Shared Builders
App Settings: Map Provider
Script Attack Protection: Whitelisted Custom Code Elements and Attributes
Script Attack Protection: Protected Areas
Security & Infrastructure
Security Best Practices
Builder Security Settings for All Knack Plans
Builder Two-Factor Authentication
Table of Contents
- All Categories
- How To Guides
- How to Create Dynamic Dropdowns in Forms
How to Create Dynamic Dropdowns in Forms
Updated by Lesley
Dynamic dropdowns, also called dependent or cascading dropdowns, are actually just two related connection fields in a form. They allow you to show values in the second dropdown field based on the selection made in the first dropdown field.
For example, a consulting company wants to create new Projects, add Tasks, and assign them to an Employee they work with. On the Add Tasks form, they only want to see the Projects connected to that particular Employee. They do not want to see all the Project records in their database.
In other words, you’ll be editing the form to only show the child records connected to the selected parent record.
If this your first time creating an app, you'll need to know some basics about adding tables, fields, pages, and views. You can start by reading our Builder Basics section.
Other good resources can be found in our designing the database and building pages sections of the knowledge base.
Add Your Tables
This article uses the Project Management template app to illustrate this example. In the Data section of the Builder, add your three tables:
You can learn more about adding tables here.
In the Data section of the Builder, navigate to the Employees table. Add a connection to the Projects table:
In Projects, add two connection fields, one to Employees and one to Tasks.
You can learn more about adding connections here.
Add some sample records to the Project and Employee tables, connecting each Project record to an Employee.
Learn more about adding and managing records here.
Add a Form
In the Pages section of the Builder, add a new page for Tasks. Include a form at add a new Task on that page:
Learn more about adding Pages and Views to your app.
Edit Form Fields
Click on your form to add a new Task to open the form's view editor:
In the Inputs section, add inputs for both connections:
Select the child connection, or Projects field. Under the Show dropdown, select the option to only show the Project records connected to the form's Employee:
Learn more about editing forms here.
Test Your Form
Go to the form you created in the Live App and select an Employee from the dropdown. Click on the Projects dropdown to ensure only the Project records you connected to the selected Employee are displayed.
When you select a different Employee, the Project records will automatically update to only show the Projects connected to the selected Employee.
Notes & Troubleshooting
If you’re not seeing the correct “Show” option:
- Make sure your connection is set up properly. You’ll want the connection to be in the child table, or the table associated with the connection field you’re editing.
- Make sure the field you are editing is a connection field.