how to get single row in select count(*) in following query postgresql

Question

select count(*) from ordrer 
inner join ordrelinjer on ordrelinjer.ordrenr = ordrer.ordrenr 
group by ordrelinjer.varetekst

This query return 4 rows, but I want to return 4 in count(*) , how to do so?

Answer 1

You are getting 4 row because of group by. If you need distinct group count, you can try subquery.

select count(*) 
from (
   select count(*) 
   from ordrer 
      inner join ordrelinjer on ordrelinjer.ordrenr=ordrer.ordrenr 
   group by ordrelinjer.varetekst
) t

Answer 2

不带分组调用

select count(*) from ordrer inner join ordrelinjer on ordrelinjer.ordrenr=ordrer.ordrenr 

Answer 3

It seem that you're looking for the distinct number of values for ordrelinjer.varetekst, which would be:

select count(distinct ordrelinjer.varetekst)
from   ordrer 
join   ordrelinjer on ordrelinjer.ordrenr = ordrer.ordrenr;