PIVOT table in SQL?

Question

Hello,
I have a table with 3 columns, where person_id is unique id.
<person_id> <event_type> <number_events>
1. I need to transform this into a table with <person_id> <event_type1> <event_type2>.... <event_type-n>
And under each column I need to fill the number_events for each event_type for that person_id
2. Next step is to use that table and convert the same into % of number_events under each event_type, as % of total number_events for each id_member
Thanks

Answer 1

1. I need to transform this into a table with <person_id> <event_type1> <event_type2>.... <event_type-n>Problem as a SQL projection cannot be of an-unknown-number-of-columns-we-will-figure-it-out-at-run-time. Unless you use some funky PL/SQL coding to create an Advance SQL Data Type that sports a RTTI interface. And this is typically t0o complex for the "normal" PL/SQL developer that almost never use Advance SQL Data Types to create SQL classes, never mind using OCI calls to define PL/SQL methods for RTTI interfaces.
You can of course have a column that is a collection - and a collection can contain any number of elements.
Example:
SQL> -- create a collection type of strings
SQL> create or replace type TStrings as table of varchar2(4000);
  2  /                                                         
Type created.
SQL>
SQL> col TYPE format a15
SQL> col NAME_LIST format a100
SQL>                         
SQL> -- now perform a pivot using a collection where
SQL> -- the collection can be 1..n                 
SQL> select                                        
  2          t.object_type as "TYPE",              
  3          cast(   multiset(                     
  4                          select object_name from user_objects n where n.object_type = t.object_type
  5                  )                                                                                
  6                  as TStrings                                                                      
  7          ) as "NAME_LIST",                                                                        
  8          count(*) as "TOTAL"                                                                      
  9  from       user_objects t                                                                        
10  group by                                                                                         
11          t.object_type                                                                            
12  order by 1                                                                                       
13  /                                                                                                
TYPE            NAME_LIST                                                                                                 TOTAL
FUNCTION        TSTRINGS('TESTPIPE', 'TO_TMINOR', 'TO_SUB', 'AUTHENTICATE', 'CHECKSUM', 'FOOPIPE', 'WEBBROWSER', 'PR         19
                EVENTDELETE', 'GETSTAT', 'GETHOSTNAME', 'FOOFUNC', 'TOKENISE', 'DYNAMICFUNCTION', 'STATS', 'POP3', '          
                CALC', 'VPDBPOLICY', 'LISTTONUMBERS', 'TCPPING')                                                              
INDEX           TSTRINGS('SYS_C0046436', 'SYS_C0046439', 'SYS_IOT_TOP_125320', 'SYS_IOT_TOP_125322', 'SYS_IOT_TOP_12         23
                5324', 'SYS_IOT_TOP_125327', 'PK_STUFF', 'SYS_C0055439', 'SYS_C0076868', 'PATIENT_PK', 'SYS_C0055021          
                ', 'INPATIENT_PK', 'SYS_C0055023', 'BED_PK', 'PK_TAB11', 'PK_ROUTERS', 'SYS_C0055202', 'PK_FOO_TAB',
                 'PK_FOO_UPDATE', 'PK_SERIALISE', 'SYS_C0058353', 'PK_EMP', 'PK_ANYCHART_TEMPLATES')
LIBRARY         TSTRINGS('LIBC')                                                                                              1
LOB             TSTRINGS('SYS_LOB0000125313C00031$$', 'SYS_LOB0000153382C00007$$', 'SYS_LOB0000141150C00002$$', 'SYS          6
                 _LOB0000205530C00001$$', 'SYS_LOB0000197183C00002$$', 'SYS_LOB0000209404C00002$$')