About Equations

What is an equation?

Equation fields function by merging field values, numbers, and other mathematical functions to construct an equation that will be calculated for each record. These fields are a specific type of field found in a table within the Data section of the Builder.

There are two equation types available: Number and Date

Numeric Equation example : (Sales - Expenses) * 12

Date Equation example : (Date Completed) - (Date Started)

Managing Equations

Adding an Equation

To add a field to a table in the Builder's Data section, start by selecting the desired table from the left menu. Next, click on the "Add Field" button located at the top of the page.

This will give you the option to choose the Equation field type from the left side of the screen:

After selecting the Equation field type, a popup will appear where you can customize the settings for your Equation field. Once you have configured the field, simply click on the "Add Field" button located at the bottom of the pop-up window.

Editing an Equation

To modify an existing equation, choose the table that includes the equation field and then select the additional options icon (represented by "...") located beside the field's name.

Deleting an Equation

To remove an equation, navigate to the table that contains the equation field and click on the additional options icon (represented by "...") next to the field's name. From the dropdown menu, select the "Delete" option.

Caution: Please note that deleting a field will result in the removal of all record values associated with that field. Therefore, it is important to confirm that this is the correct action for your app before proceeding.

Building an Equation

Equations can take many different forms. See the Equation Types section for details on these options.

To build to your equation:

• Type the name of the field directly in the formula input box.

• Use the "Fields" dropdown list to select any available fields, or

• Type numbers or mathematical operators directly into the input box.

Below the equation editor, the Example Output shows you an example output of the current formula:

Accessing Connected Fields

As with text formulas, equations give you the option of retrieving data from connected records. If you start typing the name of a field on a connected table, you'll see the available options in a list.

You can also select the "Fields" dropdown and select the field. Fields available will include any fields from the data table you are currently in and any fields from connected tables.

Note: Fields from tables connected with a many-to-many relationship will not be available since multiple connected record values exist.

Tip: Check out our quick guide on how to include connected values in equations**:How to Include Connected Values in Equations**

Using Multiple Choice Fields in Equations

Multiple choice fields can be utilized in equations, whereby these values are automatically converted into numerical values for calculation purposes.

Non-numeric characters are automatically removed and the remaining value is considered for calculation. In case there is no number left, zero will be used as the default value.

Note: Equations using multiple choice fields will not display live results, even if the multiple choice field is used in the form.

Using Yes / No Fields in Equations

Yes/No fields can be utilized in equations. In these equations, the values of No and Yes are converted to numerical values, where No is represented as 0 and Yes is represented as 1, which are then used in the equation.

Using Equations in Forms

Requirements:

1. All fields required for the equation must be included on the form. Similarly, if you are setting a value in a record rule using a formula field, that field must also be present on the form.

2. The equation must be a Numeric equation and cannot be a Date Type.

3. The equation cannot use other formulas (sum , count , etc.)

Equation fields can be incorporated into forms to create dynamic calculators that update in real time. Let's take a look at a basic example:

Note: Currently, form submissions cannot be validated using equation fields.

Operators

You can use the following operators in your equations:

• | adds
• | subtracts
• | multiples / | divides == | equals != | not equals

| greater than = | greater than or equal to 0 & Condition B > 10 ? Equation 1 : Equation 2

Note: Unfortunately, it is not feasible to evaluate whether a field "is blank" or "is not blank" within a conditional equation.

Conditional Example 1:

There may be times when you need to track total elapsed time. This could easily be done using the currentTime() function, but what happens when your date field is blank?

A blank date would be interpreted as "0", which Knack would interpret as "January 1, 1970", resulting in a very long negative number. Using a conditional rule we can make sure our equation remains "0" instead:

(Invoice Date) > 0 ? (Invoice Date) - currentTime() : 0

Conditional Example 2:

This example shows how to apply an additional 3% late fee to a charge:

(Time of Payment) > (Due Date) ? (Cost) * 1.03 : (Cost)

Conditional Example 3:

To trigger an equation when values are equal you can use the "==" operator:

(Budget Period) == 1 ? (Q1 Date) : (Budget Period)==2 ? (Q2 Date) : 0

Conditional Example 4

This complex example uses the following logic:

• If Time of Payment is later than Due Date, charge an extra 3%

• If Time of Payment is earlier than the Due Date, charge 1% less

• Otherwise (if Time of Payment equals Due Date), charge the normal amount

(Time of Payment) > (Due Date) ? ((Cost) 1.03) : ((Time of Payment) 0 & (Start Date) > 0 ? (End Date) - (Start Date) : (Start Date) > 0 ? currentTime() - (Start Date) : 0

Conditional Equations with Text Fields

Conditional rules don’t currently work with text fields, but you can map your text fields to number fields and use the number fields in your equation. Assuming you already have a short text field called Text:

1. Add a number field (we’ll call it Num).

2. Add a conditional rule to the Num for each option you want to account for Text ; e.g. set Num to "1" if Text is "First Choice", set Num to "2" if Text is "Second Choice", etc.

3. Run a batch update on your data (even on a new temporary field) to populate the Num field via its conditional rules.

4. Use Num in place of Text in your equations.

Conditional Equation with Text Fields Example

If we want the following conditions tested:

• If Text is "First Choice", ie: Num is 1, set the equation to "1"

• If Text is "Second Choice", ie: Num is 2 set equation to "2"

• If Text is anything else, set the equation to "0"

In the equation, you would need to utilize the Num field since equations cannot use text fields. Therefore, the equation would be structured as follows:

(Num) ==1 ? 1 : (Num) ==2 ? 2 : 0

Using Equations in Your App

Use Equations in Equation or Text Formula Fields

Just as in any other field on a table connected to another table, equation fields can be used in text formulas or other equation fields.

Viewing Equations in the Builder

Equation values will be displayed in the "Records" tab in a table in the Builder. Here you can view and reference these values, as well as use record filters to display particular values for this equation field.

Viewing Equations in the Live App

Except for maps, menus, and rich text views, equation fields can be added and used to display values in all** page views.**

How To Guides

• Calculate Age in Years from a Birthday

• How To Start an Auto Increment Field from Any Number

Troubleshooting

Can't Access Connected Field

If you're unable to access a connected field in a formula, check the connection between the two tables. You can only access fields from a table with a many-to-one or one-to-one relationship with the table you're adding the equation field to.

For example, let's say that many Tasks can be connected to one Project, and there's a number field called "Hourly Rate" in the Project table. You can create an equation in the Tasks table that pulls in the value from the Hourly Rate field in the Project's table because there's only one hourly rate value to pull in.

However, if you had a number field called "Hours Worked" in the Tasks table, you wouldn't be able to access that field in an equation in the Projects table. There would be multiple "Hours Worked" values to pull in and an equation field can't do that.

In a case like that, you could use a formula field to access all the connected "Hours Worked" values. Then, the formula field could be used in the equation.

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