Question

I want to select all the rows from table where date different between two row is 4 or less and stop as soon as condition don’t match ie diff > 4 in descending order i.e.(from bottom)

caution: once condition is > 4 it will not match further it simply
stops

i.e it will have to select 5,6,7,8,9

I tried using “HAVING“, but its slow on big data

Thank you all in advance to helping figure it out.

Answer 1

You can use user-defined variables to track the previous updated_at value (in my example below, in @t) then calculate from that whether the record is desired based on whether the previous record was desired (@b) and, if so, the difference between that last date and the current one:

SELECT   id, amount, updated_at
FROM (
  SELECT   my_table.*,
           @b:=IF(@b, DATEDIFF(@t,updated_at)<=4, FALSE) okay,
           @t:=updated_at
  FROM     my_table, (SELECT @b:=TRUE, @t:=MAX(updated_at) FROM my_table) init
  ORDER BY updated_at DESC
) t
WHERE    okay
ORDER BY updated_at, id

See it on sqlfiddle.