C# mysql连接查询重复返回数据

我想在c windows窗体中使用join query从mysql数据库检索数据，但它会重复给我100次数据。 这是我的密码。请帮忙

private void button2_Click(object sender, EventArgs e)
        {
            if (comboBox1.SelectedIndex < 0 || comboBox2.SelectedIndex < 0)
            {
                MessageBox.Show("Please select the Class and group");
            }
            else
            {
                table = dbOperation.select("student.admission_no, student.studid, student.name from student inner join " +
                                            "studentinclass on studentinclass.studentid = student.studid inner join " +
                                            "class on studentinclass.classid = " + comboBox1.SelectedValue + " inner join " +
                                            "`group` on studentinclass.groupid = " + comboBox2.SelectedValue + " inner join " +
                                            "section on studentinclass.sid = " + comboBox3.SelectedValue);
                listView1.Items.Clear();

                foreach (DataRow row in table.Rows)
                {
                    listView1.Items.Add(row[0].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[1].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add(row[2].ToString());
                    listView1.Items[listView1.Items.Count - 1].SubItems.Add("P");
                }
            }
        }

这是输出

---

学生ID是这两个表中的主键吗？

您需要一个子查询进行比较

要删除完整的select语句

"student.admission_no, student.studid, student.name from student " +
"where student.studid in ( select studentinclass.studentid from studentinclass " +
"inner join class on studentinclass.classid = " + comboBox1.SelectedValue + " " +
"inner join `group` on studentinclass.groupid = " + comboBox2.SelectedValue + " " +
"inner join section on studentinclass.sid = " + comboBox3.SelectedValue +")"

---

您期望的输出是什么？顺便说一句，在Select关键字后添加“DISTINCT”将帮助您消除所有重复行。dbOperation是什么类型？它是连接数据库的类的对象。只是我不希望重复。学生ID是否唯一标识两个表中的每个记录？