将多个子选择组合到一个结果行中

Question

I'm a bit stuck on this supposedly basic SQL and would appreciate some pointers.

I'd like to get a single row result from combining multiple sub-selects. What I have so far (which of course does not work):

select * from (

    (select count(*) from a where name='a') as a),
    (select count(*) from b where name='d') as b)

) as foo;

...and I'm looking for a result along the lines of:

a | b
-----
1 | 2

Given the source tables:

Table a:
 id | name
----+------
  1 | a
  2 | b
  3 | c

Table b:
 id | name
----+------
  1 | a
  2 | b
  3 | c
  4 | d
  5 | d

I also tried something along the lines of

select count(a.*), count(b.*) from a, b where a.name='a' and b.name='d';

which produces:

count | count
------+-------
    2 |     2

I'd appreciate any assistance. thanks

Answer 1

Just use:

select (select count(*) from a where name='a') as a,
       (select count(*) from b where name='d') as b