Converting number to string

[Alexander_Arozi]

HI

Im calculating the length between two dates as a number, and then i want to convert it into a string to be able to group the days. but when running the code below, I get the errormessage
“No matching signature for operator = for argument types: INT64, STRING. Supported signature: ANY = ANY”

What am I doing wrong here?
 

  dimension: date_diff_day {
    type: number
    sql: date_diff(${init_date_date},${comp_date_date},day)*-1;;
  }
  dimension:date_diff_day_string{
    type: string
    sql: ${date_diff_day} ;;
  }
  dimension: date_diff_days_grouped {
    type: string
    sql: CASE
      WHEN ${date_diff_day_string} = “1” THEN “0-1”

      …..
      ELSE ${date_diff_day_string}
      END;;
  }