为什么结果只输出了一行？

Question

select vote, sum(vote) from prolist where roomid="1" 
想输出符合条件roomid="1"的vote，以及roomid="1"的vote总和
如果单独写select vote from prolist where roomid="1"有两行

Answer 1

select vote,(select sum(vote) from prolist where roomid="1" ) as sumValfrom prolist where roomid="1

Answer 2

select vote, sum(vote) from prolist where roomid="1" group by vote