How do you do dynamic / dependent drop downs in Google Sheets?

Question

How do you get a sub-category column to populate a drop down based on the value selected in the main category drop down in google sheets?

I googled around and couldn

Answer 1

Continuing the evolution of this solution I've upped the ante by adding support for multiple root selections and deeper nested selections. This is a further development of JavierCane's solution (which in turn built on tarheel's).

/**
 * "on edit" event handler
 *
 * Based on JavierCane's answer in 
 * 
 *   http://stackoverflow.com/questions/21744547/how-do-you-do-dynamic-dependent-drop-downs-in-google-sheets
 *
 * Each set of options has it own sheet named after the option. The 
 * values in this sheet are used to populate the drop-down.
 *
 * The top row is assumed to be a header.
 *
 * The sub-category column is assumed to be the next column to the right.
 *
 * If there are no sub-categories the next column along is cleared in 
 * case the previous selection did have options.
 */

function onEdit() {

  var NESTED_SELECTS_SHEET_NAME = "Sitemap"
  var NESTED_SELECTS_ROOT_COLUMN = 1
  var SUB_CATEGORY_COLUMN = NESTED_SELECTS_ROOT_COLUMN + 1
  var NUMBER_OF_ROOT_OPTION_CELLS = 3
  var OPTION_POSSIBLE_VALUES_SHEET_SUFFIX = ""
  
  var activeSpreadsheet = SpreadsheetApp.getActiveSpreadsheet()
  var activeSheet = SpreadsheetApp.getActiveSheet()
  
  if (activeSheet.getName() !== NESTED_SELECTS_SHEET_NAME) {
  
    // Not in the sheet with nested selects, exit!
    return
  }
  
  var activeCell = SpreadsheetApp.getActiveRange()
  
  // Top row is the header
  if (activeCell.getColumn() > SUB_CATEGORY_COLUMN || 
      activeCell.getRow() === 1 ||
      activeCell.getRow() > NUMBER_OF_ROOT_OPTION_CELLS + 1) {

    // Out of selection range, exit!
    return
  }
  
  var sheetWithActiveOptionPossibleValues = activeSpreadsheet
    .getSheetByName(activeCell.getValue() + OPTION_POSSIBLE_VALUES_SHEET_SUFFIX)
  
  if (sheetWithActiveOptionPossibleValues === null) {
  
    // There are no further options for this value, so clear out any old
    // values
    activeSheet
      .getRange(activeCell.getRow(), activeCell.getColumn() + 1)
      .clearDataValidations()
      .clearContent()
      
    return
  }
  
  // Get all possible values
  var activeOptionPossibleValues = sheetWithActiveOptionPossibleValues
    .getSheetValues(1, 1, -1, 1)
  
  var possibleValuesValidation = SpreadsheetApp.newDataValidation()
  possibleValuesValidation.setAllowInvalid(false)
  possibleValuesValidation.requireValueInList(activeOptionPossibleValues, true)
  
  activeSheet
    .getRange(activeCell.getRow(), activeCell.getColumn() + 1)
    .setDataValidation(possibleValuesValidation.build())
    
} // onEdit()

As Javier says:

• Create the sheet where you'll have the nested selectors
• Go to the "Tools" > "Script Editor…" and select the "Blank project" option
• Paste the code attached to this answer
• Modify the constants at the top of the script setting up your values and save it
• Create one sheet within this same document for each possible value of the "root selector". They must be named as the value + the specified suffix.

And if you wanted to see it in action I've created a demo sheet and you can see the code if you take a copy.