c# - 关系之间的内部连接

Question

我想从三个表中获取数据:role、permission 和right。我使用了内部连接。

代码

SqlConnection con = Class3 .GetConnection();
public DataSet showoption1()
{
    string sql1 = "select  right.rightname,role.rolename
                   FROM permission
                   INNER JOIN ON right.rightid = permission.rightid
                   INNER JOIN role ON permission.roleid = role.roleid  ";
    SqlCommand cmd = new SqlCommand(sql1, con);
    SqlDataAdapter adptr = new SqlDataAdapter(cmd);
    DataSet ds = new DataSet();
    adptr.Fill(ds);
    DataTable table = ds.Tables[0];
    return ds;
}

数据库表

作用

Role Id   Role name
  1       admin
  2       employee

右

rifgtid    rightname
      1    view courses
      2    view assessmenttest

权限(关联)

permissionid    rightid     roleid
   1             1           2
   2             1           1

Answer 1

我不确定你在问什么，但是你的 sql 语法有错误

SELECT      right.rightname,
            role.rolename 
FROM        permission 
INNER JOIN  right ON right.rightid = permission.rightid 
INNER JOIN  role ON permission.roleid = role.roleid

我将 INNER JOIN ON 替换为 INNER JOIN right ON

作为旁注，处理 ADO.NET 相关对象(SqlConnection、SqlCommand、SqlDataAdapter)