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Re: querying the value of the previous row

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Chris Velevitch wrote:
I'm to write a query like:-

select
     case when column_name1 <> value_of_previous(column_name1)
          then column_name1 end as column
    ,column_name2
from table
ordered by column_name1, column_name2

in order to get:-

column        | column_name2
--------------+--------------
value_1_c1    |   value_1_c2
              |   value_2_c2
              |   value_3_c2
value_2_c1    |   value_4_c2
              |   value_5_c2
              |   value_6_c2
value_3_c1    |   value_7_c2
              |   value_8_c2
              |   value_9_c2

How do I do this? (I'm using pg 7.4)

what does 'previous' mean here?   thats not a concept SQL really has.

anyways, that sort of report output is something you usually do via your reporting code



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