Configuring a "Lookup" field, you can retrieve and copy data from a different app.
For example, you can configure a "Lookup" field in the "Order management" app in such a way that the field references data in the "Product management" app. This enables you to retrieve product information from the "Product management" app and copy the information in the "Order management" app. This reduces the effort required for entering the same data twice and prevents typing errors.
Reference: What Is Lookup?

1. Create an app to be used as a data source (reference source).
   Place some fields in the app. There is no need to register data at this point.
   

2. Open the app settings screen of the app that will retrieve data and place a "Lookup" field.

3. Open the setting screen of the "Lookup" field you have placed and configure the following setting options:

   • Name (Required)
   • The "Required field" check box
   • Datasource App (Required)
   • Key Field (Required)
     A field that plays a role of the key for associating apps. You can specify one of the following types of fields:
     "Text", "Number", "Calculated", "Lookup", "Link", and "Record number"
   • Field Mappings
   • Fields Shown in Lookup Picker
   • Initial filter setting
   • Initial sort setting
   • Field Code (Required)

   Once you save the form, you cannot change the setting for Datasource App and Key Field.
   Other setting options can be changed afterwards.
   For details on each setting, refer to "Lookup" Field Settings.

4. On the "Lookup Settings" screen, click Save.

5. Click Save Form on the upper left side of the screen.

6. If you are creating a new app, click Activate App at the upper right of the screen and click OK on the confirmation dialog.
   If you are changing the settings of an existing app, click Update App at the upper right of the screen and click Update App on the confirmation dialog.

You have successfully configured a "Lookup" field.

1. Try your lookup.
   Open the "New Record" screen of the app in which you have configured the "Lookup" field in steps 2 and 3 and click Lookup.
   When you enter a keyword and click Lookup, you can narrow down the records to only those that match the keyword.
   Reference: Using Lookup

This section uses actual apps to describe the steps to configure a lookup. In this example, the "Order management" app and "Product management" app are used.

To retrieve data of the "Product management" app (the reference source app) in the "Order management" app, you must register data that serves as a source in the "Product management" app beforehand.
In this example, data such as product code, product name, and unit price is registered beforehand.

Next, place a "Lookup" field in the "Order management" app, which will retrieve data from the other app.

1. Open the "Order management" app.

2. Click the App Settings icon (the gear-shaped icon) at the upper right of the "View" screen.
   

3. On the "App Settings" screen, click Form tab.

4. Place a "Table" field on the app form.

5. Drag and drop a "Lookup" field on the table.
   In this example, you will configure a "Lookup" field that retrieves information based on product codes.

6. Add also the fields used for displaying data retrieved from the "Product management" app to the table.
   In this example, add the following fields:

   • Product Name: "Text" field
   • Unit Price: "Number" field
   • Quantity: "Number" field
   • Subtotal: "Calculated" field

7. Hover your cursor over the top right of the "Lookup" field. When the Field Settings icon (the gear-shaped icon at the top right of the field) appears, click Settings.

8. Configure the following settings.

   • Set Name.
     In this example, enter "Product Code".
   • Set Datasource App.
     Select an app from which you want to copy data. In this example, select "Product management app."
   • Set Key Field.
     Select a field that will work as a key for finding a corresponding record. In this example, select the "Product code" field.
     For Key Field, you can specify any of the following fields:
     • "Text", "Number", "Calculated", "Lookup", "Link", and "Record number" fields

9. Select fields for Field Mappings.
   The data of multiple fields can be retrieved from the records in the reference source app at once.
   In this example, add the following pairs: "Product name" < "[Product management]Product name" and "Unit price" < "[Product management]Unit price."
   You can click the plus button (+) to add as many rows as necessary based on how many fields you want to copy.

10. If necessary, select fields for Fields Shown in Lookup Picker.
    Fields specified here are displayed on the screen to select which record you want to retrieve data from. These fields help you identify the correct record when there are multiple records with the same product code.
    In this example, select "Product name" and "Unit price." For details, refer to Using Lookup.

11. If necessary, also configure the following:

    • Specify Initial filter setting.
      This filter setting will be applied to help users select a record appropriately. From the dropdown, select a field to which the condition is to be applied, and then specify the filter condition. In this example, you will not configure the initial filter setting since you want all records to be displayed.
      Even if you have configured the initial filter setting, it is not applied when only one record matches the keyword entered into the "Lookup" field. In such a case, the information in the record is retrieved directly without the filter being applied.

    • Specify Initial sort setting.
      Specify the display order of records to be retrieved. In this example, select "Product code" and Ascending.
      

12. Click Save on the settings screen of the "Lookup" field.

13. Click Table Settings under the Table Settings icon (the gear-shaped icon at the upper right of the table), then set a table name.

14. Enter a table name and click Save.
    In this example, enter "Product information".

15. Click Save Form on the upper left side of the screen.

16. Click Update App at the upper right of the screen.

17. On the confirmation dialog, click Update App.

You have successfully configured a "Lookup" field.
For details on how to use a lookup, refer to Using Lookup.

Specifying Field Mappings in the Lookup settings, you can retrieve data of various fields, such as "Multi-choice" fields, "Check box" fields, and "Drop-down" fields.
This section explains how to copy the following data registered in the "Customer Database" app and add it in the "Lead Management" app.

• Product Name (A "Multi-choice" field)
• Options (A "Check box" field)

Since company names are registered in both the "Customer Database" app and the "Lead Management" app, you will use company names to retrieve data for products and options.
In the "Lead Management" app, place a "Lookup" field, in which you will enter a company name to lookup data, and configure the field as described below:

Now, by entering a company name in the "Lead Management" app and clicking Lookup, you can retrieve product names and options from the "Customer Database" app.

• Even if changes are made to the records that are referred to (the records in the reference source app), values that are already retrieved in the "Lookup" field remain unchanged. The values are not automatically updated.
  Users need to click Lookup again to overwrite existing data with the latest data.
  
  

• You can bulk update existing records by importing a CSV file.
  However, the field values entered using the Lookup feature can be updated only if both of the following conditions are met:

  • There are no duplicate values for the Key Field (the field specified for Key Field) in existing records.
  • The Prohibit duplicate values checkbox is selected in the settings of the field specified for Key Field.
    For example, if you specify the "Product Code" field from a product management app as the Key Field of a "Lookup" field, the "Product code" field cannot contain any duplicate values in the product management app, and the Prohibit duplicate values checkbox must be selected in the settings of the "Product Code" field.

• Any field that is set in a table cannot be specified.
  
  

• Even if you change the setting in the "Lookup" field, values in the following field of existing records do not change.

  • Fields specified for Field Mappings in the "Lookup" field setting

The following video explains how to configure a lookup using a "Customer Management" app and a "Lead Management" app.