i have a table with the columns such id, tid, companyid, ttype etc..

the id may be same for many companyid but unique within the companyid and tid is always unique and

i want to calculate the total no of transactions entered in the table,

a single transaction may be inserted in more than one row,

for example,

id tid companyid ttype 
1  1   1         xxx
1  2   1         may be null
2  3   1         yyy
2  4   1         may be null
2  5   1         may be null

the above entries should be counted as only 2 transactions ..

it may be repeated for many companyids..

so how do i calculate the total no of transactions entered in the table

i tried

select sum(count(*)) from transaction group by id,companyId; 

but doesn't work

select count(*) from transaction group by id; 

wont work because the id may be repeated for different companyids.