code: function placeholder (model, name, spec) {
      // if colum is id then needs to be wrapped in UNHEX
      if (spec.type === 'id' && model.binaryIds) {
          return `UNHEX(:${name})`
      }
      // if column is data and compression is in use it is hex
      else if (spec.type === 'data' && model.compression) {
          return `FROM_BASE64(:${name})`
      }
      else {
          return `:${name}`
      }
  }
docs: @function placeholder
  
  create placeholder for value based on column type
  
  @params {object} model
  @params {string} name
  @params {object} spec
  
  @returns {string}
  
  @throws {Error}