select "a" name, count(1)
from tableA
union
select "b" name, count(1)
from tableB
union
select "C" name, count(1)
from tableC

Use multi-column writing method

with 
temp_a as (select count(*) num from talbeA),
temp_b as (select count(*) num from tableB),
temp_c as (select count(*) num from tableC)
select temp_a.num, temp_b.num, temp_c.num from dual;

select A.countA,B.countB from (select count(*) as countA from t_countA) as A ,(select count(*) as countB from t_countB) as B

Like this?

Mysql

Oracle
Add from dual

Mysql
select table_rows from information_schema.TABLES where table_schema in ('schema1','schema2','scheman') and table_name in ('tableName1','tableName2','tableNameN')
I believe oralce also has a similar system table