How to use windowing functions to find gaps in sequences grouped by a column, in PostgreSQL





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I have a table structure which has 2 columns: client_id, order_no, and both are integers. I'd like to find gaps in order_no in the data so that, for example, for a table containing these rows:



42, 1
43, 1
42, 2
43, 5
43, 6
42, 3


the output contains the client_id, and boundaries of the gaps, like this:



43, 2, 4


Note that there's no row with client_id=42 because there are no gaps in its data.



I've tried this for the core part of the query:



select 
client_id,
order_no as start_order_no,
lead(order_no) over (order by client_id, order_no) as end_order_no


but that apparently doesn't do what I want, and I suspect it's because of client_id in the OVER part.










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  • 2





    You probably meant partition by client_id order by order_no

    – mustaccio
    Nov 1 '18 at 18:41


















0















I have a table structure which has 2 columns: client_id, order_no, and both are integers. I'd like to find gaps in order_no in the data so that, for example, for a table containing these rows:



42, 1
43, 1
42, 2
43, 5
43, 6
42, 3


the output contains the client_id, and boundaries of the gaps, like this:



43, 2, 4


Note that there's no row with client_id=42 because there are no gaps in its data.



I've tried this for the core part of the query:



select 
client_id,
order_no as start_order_no,
lead(order_no) over (order by client_id, order_no) as end_order_no


but that apparently doesn't do what I want, and I suspect it's because of client_id in the OVER part.










share|improve this question
















bumped to the homepage by Community 3 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.











  • 2





    You probably meant partition by client_id order by order_no

    – mustaccio
    Nov 1 '18 at 18:41














0












0








0








I have a table structure which has 2 columns: client_id, order_no, and both are integers. I'd like to find gaps in order_no in the data so that, for example, for a table containing these rows:



42, 1
43, 1
42, 2
43, 5
43, 6
42, 3


the output contains the client_id, and boundaries of the gaps, like this:



43, 2, 4


Note that there's no row with client_id=42 because there are no gaps in its data.



I've tried this for the core part of the query:



select 
client_id,
order_no as start_order_no,
lead(order_no) over (order by client_id, order_no) as end_order_no


but that apparently doesn't do what I want, and I suspect it's because of client_id in the OVER part.










share|improve this question
















I have a table structure which has 2 columns: client_id, order_no, and both are integers. I'd like to find gaps in order_no in the data so that, for example, for a table containing these rows:



42, 1
43, 1
42, 2
43, 5
43, 6
42, 3


the output contains the client_id, and boundaries of the gaps, like this:



43, 2, 4


Note that there's no row with client_id=42 because there are no gaps in its data.



I've tried this for the core part of the query:



select 
client_id,
order_no as start_order_no,
lead(order_no) over (order by client_id, order_no) as end_order_no


but that apparently doesn't do what I want, and I suspect it's because of client_id in the OVER part.







postgresql window-functions gaps-and-islands






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edited Nov 1 '18 at 19:03









MDCCL

6,85331745




6,85331745










asked Nov 1 '18 at 18:30









Ivan VorasIvan Voras

27019




27019





bumped to the homepage by Community 3 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.







bumped to the homepage by Community 3 mins ago


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  • 2





    You probably meant partition by client_id order by order_no

    – mustaccio
    Nov 1 '18 at 18:41














  • 2





    You probably meant partition by client_id order by order_no

    – mustaccio
    Nov 1 '18 at 18:41








2




2





You probably meant partition by client_id order by order_no

– mustaccio
Nov 1 '18 at 18:41





You probably meant partition by client_id order by order_no

– mustaccio
Nov 1 '18 at 18:41










1 Answer
1






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oldest

votes


















0














You should use a CTE or a subquery to get the lead order_no first.






select client_id,
order_no + 1 as c1,
no - 1 c2
from (select client_id,
order_no,
lead(order_no)
over (partition by client_id order by client_id, order_no) as no
from tbl) ct
where no is not null
and no - order_no > 1;






with ct as
(
select client_id,
order_no,
lead(order_no)
over (partition by client_id order by client_id, order_no) as no
from tbl
)
select client_id,
order_no + 1 as c1,
no - 1 c2
from ct
where no is not null
and no - order_no > 1;



client_id | c1 | c2
--------: | -: | -:
43 | 2 | 4



db<>fiddle here






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    1 Answer
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    active

    oldest

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    1 Answer
    1






    active

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    active

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    0














    You should use a CTE or a subquery to get the lead order_no first.






    select client_id,
    order_no + 1 as c1,
    no - 1 c2
    from (select client_id,
    order_no,
    lead(order_no)
    over (partition by client_id order by client_id, order_no) as no
    from tbl) ct
    where no is not null
    and no - order_no > 1;






    with ct as
    (
    select client_id,
    order_no,
    lead(order_no)
    over (partition by client_id order by client_id, order_no) as no
    from tbl
    )
    select client_id,
    order_no + 1 as c1,
    no - 1 c2
    from ct
    where no is not null
    and no - order_no > 1;



    client_id | c1 | c2
    --------: | -: | -:
    43 | 2 | 4



    db<>fiddle here






    share|improve this answer




























      0














      You should use a CTE or a subquery to get the lead order_no first.






      select client_id,
      order_no + 1 as c1,
      no - 1 c2
      from (select client_id,
      order_no,
      lead(order_no)
      over (partition by client_id order by client_id, order_no) as no
      from tbl) ct
      where no is not null
      and no - order_no > 1;






      with ct as
      (
      select client_id,
      order_no,
      lead(order_no)
      over (partition by client_id order by client_id, order_no) as no
      from tbl
      )
      select client_id,
      order_no + 1 as c1,
      no - 1 c2
      from ct
      where no is not null
      and no - order_no > 1;



      client_id | c1 | c2
      --------: | -: | -:
      43 | 2 | 4



      db<>fiddle here






      share|improve this answer


























        0












        0








        0







        You should use a CTE or a subquery to get the lead order_no first.






        select client_id,
        order_no + 1 as c1,
        no - 1 c2
        from (select client_id,
        order_no,
        lead(order_no)
        over (partition by client_id order by client_id, order_no) as no
        from tbl) ct
        where no is not null
        and no - order_no > 1;






        with ct as
        (
        select client_id,
        order_no,
        lead(order_no)
        over (partition by client_id order by client_id, order_no) as no
        from tbl
        )
        select client_id,
        order_no + 1 as c1,
        no - 1 c2
        from ct
        where no is not null
        and no - order_no > 1;



        client_id | c1 | c2
        --------: | -: | -:
        43 | 2 | 4



        db<>fiddle here






        share|improve this answer













        You should use a CTE or a subquery to get the lead order_no first.






        select client_id,
        order_no + 1 as c1,
        no - 1 c2
        from (select client_id,
        order_no,
        lead(order_no)
        over (partition by client_id order by client_id, order_no) as no
        from tbl) ct
        where no is not null
        and no - order_no > 1;






        with ct as
        (
        select client_id,
        order_no,
        lead(order_no)
        over (partition by client_id order by client_id, order_no) as no
        from tbl
        )
        select client_id,
        order_no + 1 as c1,
        no - 1 c2
        from ct
        where no is not null
        and no - order_no > 1;



        client_id | c1 | c2
        --------: | -: | -:
        43 | 2 | 4



        db<>fiddle here







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 1 '18 at 21:55









        McNetsMcNets

        16.4k42261




        16.4k42261






























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