求一个group的sql查询，标题要长点
表table
id name group leader
1 aa 一组 0
2 bb 一组 1
3 cc 二组 0
4 dd 二组 1
5 ee 二组 0
6 ff 三组 0
7 gg 三组 0

返回
id name group leader 统计
2 bb 一组 1 2
4 dd 二组 1 3
6 ff 三组 0 2

说明
按group分组，取出每组中第一条数据，优先取leader=1的，没有则取id最小的，并统计每组成员人数
不知道说清楚没有，求大神 sql
[解决办法]

with tb (id, name, [group], leader)as(
select 1,  'aa', '一组',  0 union all
select 2,  'bb', '一组',  1 union all
select 3,  'cc', '二组',  0 union all
select 4,  'dd', '二组',  1 union all
select 5,  'ee', '二组',  0 union all
select 6,  'ff', '三组',  0 union all
select 7,  'gg', '三组',  0),
tbb as(
select *,row_number() over(partition by [group] order by leader desc,id  ) number from tb)
select id,name,[group],leader,
(select count([group]) from tbb where a.[group]=[group]) 统计 from tbb a where number=1
order by id

[解决办法]
select *,统计=(select COUNT(1) from tb t2 where t2.[group]=t1.[group]) from tb t1 where id= (select top 1 id from tb t2 where t2.[group]=t1.[group] order by t2.leader desc,t2.id asc)