Warning! It depends on the statistics and could be not accurate!

Sybase

select user_name( obj.uid), obj.name , rowcnt(doampg)
from sysindexes idx, sysobjects obj
where idx.indid < 2 and idx.id = obj.id and obj.type = 'U'
order by 1,2
go

select object_name( idx.id ), rowcnt(doampg)
from sysindexes idx
where idx.indid < 2
and object_name( idx.id ) in ('object1','object2')
go


Oracle

select OWNER, TABLE_NAME, NUM_ROWS
from dba_tables
where TABLE_NAME = upper( '&what_tbl.' );

select OWNER, TABLE_NAME, NUM_ROWS
from dba_tables
order by 1,2;