What is the best way to populate a dropdown ?

Question

I need the managers list while adding an employee . i have an employee and manager table . 
 while creating an employee , i need to populate managers list so that HR can assign the manager to an employee . in the interface i need to populate the Manager dropdown . 
 
 Option 1 
 
 --Create a query entity to fetch all the managers 
 --get the data subset 
 -- initialize local!managers:rule!getManagers() 
 and display like below 
 a!dropdownField( label: "Manager", labelPosition: "ADJACENT", placeholderLabel: "--- Select a Manager ---", choiceLabels:{index(local!managers.data,"name")}, choiceValues:{index(local!managers.data,"name")}, value: ri!manager.name, saveInto: ri!manager.id, validations: {} ) 
 
 are there any better approach ?

Josh · Accepted Answer

This error indicates that an id in your list is null. While the "value" of a dropdown can be null, none of your "choiceValues" can be null. 
 
Assuming the "id" is a primary key of your manager table, I wouldn&#x27;t expect any of your ids to be null. I would look into the data being returned.

sonakshid · Answer

I agree with vahedullas, database interactions/queries should be done in process model and passed as rule inputs to SAIL, 
as it will reduce form rendering time to the user and improves SAIL performance. 
 
Also, in case if large data present in database, querying on SAIL impacts performance.

Josh · Answer

Your snippet should look more like 
 
 a!dropdownField(
 label: "Manager",
 labelPosition: "ADJACENT",
 placeholderLabel: "--- Select a Manager ---",
 choiceLabels:{index(local!managers.data, "name", {})},
 choiceValues:{index(local!managers.data, "id", {})},
 value: index(ri!manager, "id", null),
 saveInto: ri!manager.id,
 validations: {}
) 
 
 If your query doesn't take too much time, loading the managers in a load() variable on the interface will be fine. However, this load variable will re-evaluate whenever the user opens up the interface, so if you anticipate both the user frequently leaving/coming back to the form AND the query is slow, I would store the data in process and pass the list in as a rule input.