MySQL - Få en tæller for hver dubletværdi

MySQL har desværre ikke vinduesfunktioner, hvilket er hvad du skal bruge. Så du bliver nødt til at bruge noget som dette:

Endelig forespørgsel

select data, group_row_number, overall_row_num
from
(
  select data,
        @num := if(@data = `data`, @num + 1, 1) as group_row_number,
        @data := `data` as dummy, overall_row_num
  from
  (
    select data, @rn:[email protected]+1 overall_row_num
    from yourtable, (SELECT @rn:=0) r
  ) x
  order by data, overall_row_num
) x
order by overall_row_num

se SQL Fiddle with Demo

Forklaring:

Først, indre markering, dette anvender et falsk row_number til alle posterne i din tabel (se SQL Fiddle with Demo ):

select data, @rn:[email protected]+1 overall_row_num
from yourtable, (SELECT @rn:=0) r

Anden del af forespørgslen, sammenligner hver række i din tabel med den næste for at se, om den har samme værdi, hvis den ikke starter, så starter group_row_number over (se SQL Fiddle with Demo ):

select data,
      @num := if(@data = `data`, @num + 1, 1) as group_row_number,
      @data := `data` as dummy, overall_row_num
from
(
  select data, @rn:[email protected]+1 overall_row_num
  from yourtable, (SELECT @rn:=0) r
) x
order by data, overall_row_num

Det sidste valg returnerer de værdier, du ønsker, og placerer dem tilbage i den rækkefølge, du anmodede om:

select data, group_row_number, overall_row_num
from
(
  select data,
        @num := if(@data = `data`, @num + 1, 1) as group_row_number,
        @data := `data` as dummy, overall_row_num
  from
  (
    select data, @rn:[email protected]+1 overall_row_num
    from yourtable, (SELECT @rn:=0) r
  ) x
  order by data, overall_row_num
) x
order by overall_row_num