I want a count of distinct rows in a table

Question

I want a count of distinct rows in a table through a single query -- is it possible?
eg.
table-
create table ch1 (a int, b int, c int, d int)
insert ch1 values (1,1,1,1)
insert ch1 values (2,2,2,2)
insert ch1 values (1,1,1,1)
insert ch1 values (2,2,2,2)
insert ch1 values (1,3,4,5)

Answer 1

hi,
create table ch1 (a int, b int, c int, d int) ;
insert into  ch1 values (1,1,1,1);
insert into  ch1 values (2,2,2,2);
insert  into  ch1 values (1,1,1,1);
insert into  ch1 values (2,2,2,2);
insert into  ch1 values (1,3,4,5);
SQL> select * from ch1;
         A          B          C          D
         1          1          1          1
         2          2          2          2
         1          1          1          1
         2          2          2          2
         1          3          4          5
SQL> select distinct * from ch1;
         A          B          C          D
         1          1          1          1
         1          3          4          5
         2          2          2          2
SQL>
  1* select count(*) from( select distinct * from ch1)
SQL> /
  COUNT(*)
         3
SQL> ed
Wrote file afiedt.buf
  1   select count(*) from (select a,b,c,d  from ch1
  2* group by a,b,c,d)
SQL> /
  COUNT(*)
         3
SQL> Thanks,
P Prakash