MySQL make it recognize 0 is less than A in case statement

Question

I wrote a case statement returning if ladder_value_lh2 is < or > ladder_value_lh1:

    CASE
        WHEN ladder_value_lh1>ladder_value_lh2 THEN 'up'
        WHEN ladder_value_lh1< ladder_value_lh2 THEN 'down'
        WHEN ladder_value_lh2 IS NULL THEN 'No Change'
        END AS advocacy_moved_up_down_nochange,

Ladder values are made up of 0, A, B, C1, C2, D, and E.

Right now, it doesn't recognize that 0 is less than A (etc). So, if ladder_value_lh1 is 0, and less than ladder_value_lh2 of B, I'd expect down; right now, it's returning 'No Change'.

How do I tell it that 0 is less than A (etc)?

THanks

Answer 1

I would suggest you use field() s:

(case sign(field(ladder_value_lh1, '0', 'A', 'B', 'C1', 'C2', 'D', 'E') - field(ladder_value_lh2, '0', 'A', 'B', 'C1', 'C2', 'D', 'E'))
      when 1 then 'up'
      when -1 then 'down'
      when 0 then 'no change'
      else 'null value'
 end)