need to convert data in multiple rows with same ID into 1 row with multiple columns

问题

I reviewed versions of my question already addressed, but some of the good tips I found (using rank() over (partition...) for example, do not seem to work in the Sybase version I am on.

I am hoping to run a procedure that pulls data organized as follows:

Email | Preference
email1 | PreferenceXYZ
email1 | PreferenceABC

And render it in a table like the following:

Email | Preference1 | Preference2
email1 | PreferenceXYZ | PreferenceABC

In essence, I have multiple records for the same person (best identified via email record as a unique identifier) and I want to capture these multiple preferences for a given user and create 1 individual record per user (per email).

回答1:

If you only have two preferences, then you can use min() and max():

select email, min(preference) as preference1,
       (case when min(preference) <> max(preference) then max(preference) end) as preference2
from t
group by email;

EDIT:

If you have up to seven values, then pivot using row_number():

select email,
       max(case when seqnum = 1 then preference end) as preference1,
       max(case when seqnum = 2 then preference end) as preference2,
       max(case when seqnum = 3 then preference end) as preference3,
       max(case when seqnum = 4 then preference end) as preference4,
       max(case when seqnum = 5 then preference end) as preference5,
       max(case when seqnum = 6 then preference end) as preference6,
       max(case when seqnum = 7 then preference end) as preference7
from (select t.*, row_number() over (partition by email order by preference) as seqnum
      from t
     ) t
group by email;

EDIT II:

You can actually do this with a correlated subquery instead of row_number():

select email,
       max(case when seqnum = 1 then preference end) as preference1,
       max(case when seqnum = 2 then preference end) as preference2,
       max(case when seqnum = 3 then preference end) as preference3,
       max(case when seqnum = 4 then preference end) as preference4,
       max(case when seqnum = 5 then preference end) as preference5,
       max(case when seqnum = 6 then preference end) as preference6,
       max(case when seqnum = 7 then preference end) as preference7
from (select t.*,
             (select count(*)
              from t t2
              where t2.email = t.email and
                    t2.preference <= t.preference
             ) as seqnum
      from t
     ) t
group by email;

来源：https://stackoverflow.com/questions/20726119/need-to-convert-data-in-multiple-rows-with-same-id-into-1-row-with-multiple-colu

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