Need to understand the Cascading of Drop down concept when data is from DB tables.

This is my Raw code

a!localVariables(
local!vehicleTypeData:rule!FF_Exp_VehiclesTypes(VehicleId:null),
local!vehicleSubTypeData:rule!FF_Exp_VehiclesSubTypes(subId:null),
local!vehicleType,
local!vehicleSubType,
{
a!dropdownField(
label: "Dropdown",
labelPosition: "ABOVE",
placeholder: "--- Select a Value ---",
choiceLabels: local!vehicleTypeData.category,
choiceValues: local!vehicleTypeData.id,
saveInto: {},
searchDisplay: "AUTO",
validations: {}
),
a!dropdownField(
label: "Dropdown",
labelPosition: "ABOVE",
placeholder: "--- Select a Value ---",
choiceLabels: local!vehicleSubType,
choiceValues: local!vehicleSubType,
saveInto: {},
searchDisplay: "AUTO",
validations: {}
)
})

Hi Faisal,

The code below is just a reference for help you to implement your final solution. It is a working code, but the values in the locals are map instead queries.  As Peter explained, you just need to replace the value in the local variables for your queries an use the selected vehicle id as a filter in the second query(subcategory).

a!localVariables(
  local!selectedVehicleId,
  local!vehicle: 
    {
      a!map( id:1, value:"Cars" ),
      a!map( id:2, value: "Buses" ),
      a!map( id:3, value: "Trains"   )
  },  
  local!subCategory: {
    a!map( subTypeId:1, vehicleTypeId: 1, value: "Sedan" ),
    a!map( subTypeId:2, vehicleTypeId: 1, value: "Suv" ),
    a!map( subTypeId:3, vehicleTypeId: 2, value: "Luxury" ),
    a!map( subTypeId:4, vehicleTypeId: 2, value: "Semi Luxury" ),
    a!map(subTypeId:5, vehicleTypeId: 3, value: "Ac Trains" ),
    a!map( subTypeId:6, vehicleTypeId: 3, value: "Non Ac Trains" ),
  },  
  local!subType: if(
    isnull(local!selectedVehicleId),
    null,    
    index(local!subCategory,wherecontains(local!selectedVehicleId,tointeger(local!subCategory.vehicleTypeId)),null)
  ),
  local!selectedSubType,
  {    
    a!dropdownField(
      label: "Vehicle Type",
      labelPosition: "ABOVE",
      value: local!selectedVehicleId,
      placeholder: "Please select a vehicle",
      choiceLabels: local!vehicle.value,
      choiceValues: local!vehicle.id,
      saveInto: {
        a!save(local!selectedVehicleId,save!value),
        a!save(local!selectedSubType,null)
      }
    ),
    a!dropdownField(
      label: "Vehicle Sub Category",
      labelPosition: "ABOVE",
      value: local!selectedSubType,
      placeholder: "Please Vehicle Sub Category",
      choiceLabels: local!subType.value,
      choiceValues: local!subType.subTypeId,
      saveInto: {
        a!save(local!selectedSubType,save!value)
      }
    )
  }  
)

Hope it help you to achieve your goal,

Cheers,

Acacio B.