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Asked: 2026-05-25T09:31:21+00:00

I wanted to get the latest 4 dates for each symbolid . I adapted

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I wanted to get the latest 4 dates for each symbolid. I adapted the code here as follows:

set @num := 0, @symbolid := '';
select symbolid, date,
@num := if(@symbolid = symbolid, @num + 1, 1) as row_number,
@symbolid := symbolid as dummy
from projections
group by symbolid, date desc
having row_number < 5

and get the following results:

symbolid                date   row_number   dummy       
1       '2011-09-01 00:00:00'       1       1
1       '2011-08-31 00:00:00'       3       1
1       '2011-08-30 00:00:00'       5       1
2       '2011-09-01 00:00:00'       1       2
2       '2011-08-31 00:00:00'       3       2
2       '2011-08-30 00:00:00'       5       2
3       '2011-09-01 00:00:00'       1       3
3       '2011-08-31 00:00:00'       3       3
3       '2011-08-30 00:00:00'       5       3
4       '2011-09-01 00:00:00'       1       4
...

The obvious question is, why did I only get 3 rows per symbolid, and why are they numbered 1,3,5? A few details:

  1. I tried both forcing an index and not (as seen here), and got the same results both ways.
  2. The dates are correct, i.e., the listing correctly shows the top 3 dates per symbolid, but the row_number value is off
  3. When I don’t use the “having” statement, the row numbers are correct, i.e., the most recent date is 1, the next most recent is 2, etc

Obviously the row_number computed field is being affected by the “having” clause, but I don’t know how to fix it.

I realize that I could just change the “having” to “having row_number < 7” (6 gives the same as 5), but it’s very ugly and would like to know what to do to make it “behave”.

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1 Answer

  1. Editorial Team

    I’m not 100% sure why it behaves this way (maybe it’s because logically SELECT is processed prior to ORDER BY), but it should work as expected:

    SELECT * 
FROM 
(
    select symbolid, date,
    @num := if(@symbolid = symbolid, @num + 1, 1) as row_number,
    @symbolid := symbolid as dummy
    from projections
    INNER JOIN (SELECT @symbolid:=0)c
    INNER JOIN (SELECT @num:=0)d
    group by symbolid, date desc

) a
WHERE row_number < 5
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