数据挖掘预测中的存储过程

Question

我正在尝试编写一个存储过程来显示（fid，name，tel，income，balance，loan_amount，child_count）来自两个表 家庭（FID，姓名，电话，收入，good_credit，平衡） 儿童（CID，姓名，年龄，FID）。该功能应该能够根据以下标准预测谁可以成为潜在客户： 良好的信用，余额＆gt; = 3000，child_count：18至22岁之间的子女总数，收入：40000和loan_amount =收入* 0.3 * child_count

      Family table
      fid  name  tel   income  good_credit balance
      1    aaa1  111   15000    1           1000
      2    aaa2  211   25000    0           10000
      3    aaa3  311   80000    0           1000
      4    aaa4  411   40000    1           7000

      Children table
      cid   name    age   fid
      1     bbb1     14    3
      2     bbb2     14    15
      3     bbb3     19    16
      4     bbb4     18    9

我的代码看起来像这样，但我收到错误“子查询返回多行”

      delimiter $$
      CREATE PROCEDURE procc()
      BEGIN
      declare loan_amount int (200);
      declare child_count int (200);
      set child_count = (select count(age) from Children,Family where age             between 18 and 22 );
      set loan_amount = (select income from Children CV,Family DV where   DV.FID = CV.FID);
      if (child_count is not null) then select cf.FID as FID, cf.Name as         Name, cf.TEL as TEL, cf.income as income, cf.balance as balance, child_count, loan_amount * 0.3 * child_count from Family  cf,Children cc
     where cf.FID = cc.FID and good_credit = 1 and income >= 40000 and       balance = 3000;
     end if;
     end$$
     delimiter ;