remove duplicate values of only one column value from all the available columns in sql query

问题

I have a sql query with three columns .I want to remove any duplicate value exits in beam_current column.How to do so.I work in sql-server2012

I used Distinct but then also I'm getting duplicate values of beam_current. My sql Query is-

select DISTINCT (beam_current), logtime, beam_energy 
from INDUS2_BDS.dbo.DCCT 
where logtime between '2014-08-09 01:13:03' and '2014-08-09 02:16:53'
      and (beam_current like '%9.96' 
           or beam_current like '%9.97' 
           ... etc ...) 
      and beam_energy between '550' and '552'

EDIT-1 My output is-

In first column 29.98 is repeating thrice.I only want any one of the row corresponding to 29.98.How to do that??

回答1:

This will return 1 row for each value of beam_current:

;WITH CTE AS
(
SELECT
  row_number() over (partition by beam_current order by (select 1)) rn,
  beam_current, logtime, beam_energy 
FROM INDUS2_BDS.dbo.DCCT 
WHERE 
  logtime between '2014-08-09 01:13:03' and '2014-08-09 02:16:53'
  and (beam_current like '%9.96' or beam_current like '%9.97' 
       or beam_current like '%9.98' or  beam_current like '%9.99'
       or beam_current like '%0' or beam_current like '%_0.01' 
       or beam_current like '%_0.02' or beam_current like '%_0.03' 
       or beam_current like '%_0.04' or beam_current like '%_0.05' 
       or beam_current like '%_0.06') 
       and beam_energy between 550 and 552
)
SELECT beam_current, logtime, beam_energy 
FROM CTE
WHERE rn = 1

回答2:

The distinct keyword works on the entire row (all columns), so:

select DISTINCT (beam_current), logtime, beam_energy

is the same as:

select DISTINCT beam_current, logtime, beam_energy

is the same as:

select DISTINCT ((beam_current)), (logtime), (((((beam_energy)))))

You can use row_number() to select only the latest row per value of beam_energy:

select  *
from    (
        select  row_number() over (
                    partition by beam_current
                    order by logtime desc) as rn
        ,       *
        from    INDUS2_BDS.dbo.DCCT 
        where   logtime between '2014-08-09 01:13:03' and '2014-08-09 02:16:53'
                and (beam_current like '%9.96' 
                    or beam_current like '%9.97' 
                    ... etc ...) 
                and beam_energy between '550' and '552'
        ) numbered_rows
where   rn = 1 -- Latest row per beam_current

回答3:

It seems a single row combination is distinct for each value of beam_current. If you will try only select Distinct(beam_current) from INDUS2_BDS.dbo.DCCT where .... then only you will get that unique value.

Group by will also not work because it will group the columns from left to right written after group by keyword.So anyhow you will get the same result.

来源：https://stackoverflow.com/questions/28694871/remove-duplicate-values-of-only-one-column-value-from-all-the-available-columns

标签

sql-server

distinct-values