To find the percentage of transaction

Question

SQL> select * from txn;
tid | item
-----+------
1 | A
1 | B
1 | D
2 | A
2 | C
2 | C
2 | B
3 | A
3 | C
4 | A
4 | B
4 | C
5 | A
6 | A
7 | A
above is the table txn, how to find out the percentage of transactions that had items 'A' and 'C' (you can have multiple items per transaction id)

Answer 1

If you are trying to get the percentage of simultaneous existence of A and B for same id, you can use like...
sql>
select *
from test_tab
order by 1,2;
ID TXN 
1  A 
1  B 
1  D 
2  A 
2  C 
3  A 
3  C 
4  A 
4  B 
4  C 
5  A 
6  A 
7  A 
--So the percentage of A and C is 3/7
sql>
select (sum(decode(cnt,1,0,2))/2)/count(*) pct_of_a_and_c
from(
    select id ,sum(decode(txn,'A',1,'C',1,0)) cnt
    from test_tab
    group by id
PCT_OF_A_AND_C 
.428571429
jeneesh
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        jeneesh