Query returning duplicate rows - sql

Question

I wrote this query
SELECT DISTINCT
F2_FILIAL, F2_SERIE, F2_DOC,
C6_NUM, AB7_NUMOS, A1_NOME, F2_EMISSAO, F2_VALBRUT, F2_VEND1,
A3_NOME,F2_COND , E4_DESCRI, C5_NATUREZ, ED_DESCRIC, AAG_DESCRI
FROM
SF2010 SF
LEFT JOIN
SE4010 SE ON F2_COND = E4_CODIGO
LEFT JOIN
SA3010 A3 ON F2_VEND1 = A3_COD
LEFT JOIN
SA1010 A1 ON F2_CLIENTE = A1_COD
LEFT JOIN
SD2010 SD ON F2_DOC = D2_DOC
LEFT JOIN
SC6010 C6 ON D2_PEDIDO = C6_NUM
LEFT JOIN
SC5010 C5 ON D2_PEDIDO = C5_NUM
LEFT JOIN
SED010 ED ON C5_NATUREZ = ED_CODIGO
LEFT JOIN
AB7010 AB ON SUBSTRING(C6_NUMOS,1,6) = AB7_NUMOS
LEFT JOIN
AAG010 AG ON AB7_CODPRB = AAG_CODPRB
WHERE
(F2_CLIENTE >= ' '
AND F2_CLIENTE <= 'zzzzzz')
AND (F2_EMISSAO >= '20170222'
AND F2_EMISSAO <= '20170222')
AND (F2_VEND1 >= ''
AND F2_VEND1 <= 'zz')
AND (C5_NATUREZ >= ''
AND C5_NATUREZ <= 'zzzzzzzzzz')
AND (F2_COND >= ''
AND F2_COND <= 'zzz')
AND (F2_FILIAL >= ''
AND F2_FILIAL <= 'zz')
AND (SF.D_E_L_E_T_ <> '*')
AND F2_DUPL <> ''
AND F2_VALFAT <> 0
ORDER BY
F2_VEND1, F2_EMISSAO
And it results in something like this:
Notice that the 2 last rows are the same (the main field here is F2_DOC, it should never appear twice), but since the field C6_NUM and AB7_NUMOS has more than one reference it displays both of them, duplicating the row.
How can I improve my query to not duplicate a row when the table I'm joining has more than 1 distinct FK to the table I'm querying?

Answer 1

If you are doing multiple left joins and the leftest table in the join doesn't have ( or not mentioned in select ) a unique value, it's possible you get duplicate rows. if you need to have a unique column, use the primary key in the leftest table inside the select statement or add a column like
row_number() as id
to your query.