Do you mean something like this: ``` update t0 set b = coalesce((select b from t0 as s where a == t0.a and idate < t0.idate and b != '' order by idate desc limit 1), b) where b == '' ; ```
Do you mean something like this: ``` update t0 set b = coalesce((select b from t0 as s where a == t0.a and idate < t0.idate and b != '' order by idate desc limit 1), b) where b == '' ; ```