sqloracle-databasedynamic-sqldynamic-pivot

Dynamically create columns in select SQL Oracle


I want to show the investigator's name and title in one row.

How can I make the title column as title1, title2, title 3, or so on dynamically in SQL Oracle?

The number of titles can vary so if there is an investigator with 4 titles, then there would be 4 columns title1, title2, title3, title4.

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This is my current query:

SELECT al.name, al.title_name FROM INVESTIGATOR a1


Solution

  • There is no max number for titles but by looking at the data I think I can set it to a fixed number

    If you can pick a maximum number of titles then you don't need to do this dynamically.

    If you apply a ranking to each title for each name, with something like:

    select name,
      title_name,
      dense_rank() over (partition by name order by title_name) as rnk
    from investigator
    

    which puts them in alphabetic order, but you can choose a different order if you prefer; then you pivot the result of that query:

    select *
    from (
      select name,
        title_name,
        dense_rank() over (partition by name order by title_name) as rnk
      from investigator
    )
    pivot (
      max(title_name)
      for (rnk) in (
        1 as title1, 2 as title2, 3 as title3, 4 as title4
      )
    )
    

    I've gone with a maximum of four titles, but you can add as many as you think you might reasonably need.

    how can I name my columns Title1, title2, title3...

    I've done that using aliases in the pivot's in() clause.

    With your example data that gives output:

    NAME TITLE1 TITLE2 TITLE3 TITLE4
    ---- ------ ------ ------ ------
    Abu  AP     AR     AS
    Cu   TA
    Gyu  AP
    

    If you aren't on 11g or higher then you can do a manual pivot, which is essentiuall what Oracle is doing behind the scenes anyway:

    select name,
      max(case when rnk = 1 then title_name end) as title1,
      max(case when rnk = 2 then title_name end) as title2,
      max(case when rnk = 3 then title_name end) as title3,
      max(case when rnk = 4 then title_name end) as title4
    from (
      select name,
        title_name,
        dense_rank() over (partition by name order by title_name) as rnk
      from investigator
    )
    group by name
    

    which gets the same result.

    db<>fiddle