sql server从表中选择百分比，并从另一个表中选择所有数据

Question

i have two tables (families) and (children ) that related by family id ... every family has more than one child .. i use percentage to select families from families table and i want to know count of children to each family selected ... but when i use percentage the program return children count by percentage ... so how can i select percentage from families and all children that related to families ... my query is

select count(*) Children from 
    (select top('" + int.Parse(percentCb2.Text) + "') percent 
     f.family_id ,
     f.economic_state 
     from families f inner join Children c on c.family_id = f.family_id 
     where f.economic_state = 'b')fq 
     group by fq.family_id      

Answer 1

You are going to need to take the top families, and THEN do the join

SELECT COUNT(*) Children 
FROM
    (SELECT top('" + int.Parse(percentCb2.Text) + "') percent 
     f.family_id ,
     f.economic_state 
     FROM families
     WHERE f.economic_state = 'b') f
INNER JOIN Children c on c.family_id = f.family_id 
GROUP BY fq.family_id