如何用 MySQL 中以前的非零值替换零值？

Question

Disclaimer: This is not a duplicate question. I have research before posting

The value in red circle should have "2" value, because the previous non-zero value is number 2. how to do that in mysql update query ? as you can see there are other rows that has the same zero value that needs to be having the previous non-zero value.

Answer 1

You could use an inline query:

select 
    pk,
    case when val1 = 0 
        then (select val1 from mytable t1 where t1.pk < t.pk and t1.val1 != 0 order by pk desc limit 1)
        else val1
    end val1,
    val2,
    val3,
    received_date
from mytable t

Answer 2

If you only want to select the correct values use

  select pk, val1, @previous as previous_v, @previous := val1
  from your_table
  cross join (select @previous := 0) p
  order by pk

If you also want to update the table use

update your_table t
join
(
  select pk, val1, @previous as previous_v, @previous := val1
  from your_table
  cross join (select @previous := 0) p
  order by pk
) tmp on tmp.pk = t.pk
set t.val1 = previous_v
where t.val1 = 0

SQLFiddle demo