c# 多表查询，并写入到另一个表中解决办法

c# 多表查询，并写入到另一个表中
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现在有表：biao1,biao2,biao3

biao1至biao9都有liushuihao这个字段

biao1至biao9包含很多条数据

根据liushuihao 把biao1里面所有jine的和，加biao2里面所有jine的和，加biao3里面所有feiyong的和

算出总计后在复制给string

[解决办法]

C# code

string strSQL = "select sum(t1.jine)+sum(t2.jine)+sum(t3.feiyong) as total from biao1 t1,biao2 t2,biao3 t3where t1.liushuihao =t2.liushuihao and t1.liushuihao = t3.liushuihao and t2.liushuihao =t3.liushuihao";int ret = 0;using(SqlConnection con = new SqlConnection("Data Source=.;uid=sa;pwd=sa;Database=xxx")){   con.Open();   using(SqlCommand cmd = new SqlCommand(strSQL,con))   {       ret = (int)cmd.ExecuteScalar();   }}string s = "总金额为:"+ret.ToString();