Hi,

I am trying to count the number of distinct combinations in a table but the query gives error.

For example,

create table t(a varchar2(10), b varchar2(10), c varchar2(10));
insert into t values('a','b','c');
insert into t values('d','e','f');
insert into t values('g','h','i');
insert into t values('j','k','l');

select distinct a,b,c from t;
---4 rows
select count(distinct a,b,c) from t;
error: invalid number of arguments

If I concatenate the columns like below, it works fine, can you please explain this behaviour.

select count(distinct a||b||c) from t;
---4

Regards,
Rajneesh

select count(*)
from 
  ( select distinct a,b,c from t )