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語法。我正在使用C＃MYsql的。我有查詢，如果我對MySQL工作臺投放效果，但在C＃它不返回任何值，也沒有給螞蟻錯誤too.There只有一個不同使用MySQL的我以前的表名databaseName.tableName使用，但在C＃中，我認爲它不`噸必要。 這是查詢不返回任何內容的一部分。MySQL的：使用C＃
編輯：解決
"(select Lesson_Name from schedule where Group_NO = (select Group_NO from sinif inner join student ON sinif.Group_ID=student.Group_ID where Student_Name=(?Student))"+
" And Day_Name =(select Day_Name from day inner join date ON day.Day_ID=date.DayName where Date=(?Date))" +
"And Lesson_Time= (select Lesson_Time from clock where Lesson_Time <= (?Time)order by Lesson_Time DESC limit 0, 1) " +
" And Week_NO = (select Week_NO from week inner join date ON week.Week_ID=date.Week_ID where Date=(?Date)))
，在這裏它執行時，用戶點擊按鈕的所有代碼。
private void check_B_Click(object sender, EventArgs e)
{
connection.Open();
for (int i = 0; i < existingStudents.Count; i++)
{
MySqlCommand cmd1 = new MySqlCommand("select Student_Name,Student_Surname,Student_MacAddress from student ", connection);
MySqlCommand cmd2 = new MySqlCommand("insert into check_list (Student,Mac_Address,Date,Time,Lesson_Name)"+
"values((?Student),(?MacAddress),(?Date),(?Time),"+
"(select Lesson_Name from schedule where Group_NO = (select Group_NO from sinif inner join student ON sinif.Group_ID=student.Group_ID where Student_Name=(?Student))"+
" And Day_Name =(select Day_Name from day inner join date ON day.Day_ID=date.DayName where Date=(?Date))" +
"And Lesson_Time= (select Lesson_Time from clock where Lesson_Time <= (?Time)order by Lesson_Time DESC limit 0, 1) " +
" And Week_NO = (select Week_NO from week inner join date ON week.Week_ID=date.Week_ID where Date=(?Date))))", connection);
MySqlParameter param1 = new MySqlParameter();
param1.ParameterName = "?Student";
reader = cmd1.ExecuteReader();
if (reader.HasRows)
while (reader.Read())
{
if (reader["Student_MacAddress"].ToString() == existingStudentsMac[i].ToString())
param1.Value = reader["Student_Name" ]+" "+reader["Student_Surname"];
}
reader.Close();
MySqlParameter param2 = new MySqlParameter();
param2.ParameterName = "?MacAddress";
param2.Value = existingStudentsMac[i];
MySqlParameter param3 = new MySqlParameter();
param3.ParameterName = "?Date";
param3.Value = DateTime.Today.Date;
MySqlParameter param4 = new MySqlParameter();
param4.ParameterName = "?Time";
param4.Value = DateTime.Now.ToString("HH:mm");
cmd2.Parameters.Add(param1);
cmd2.Parameters.Add(param2);
cmd2.Parameters.Add(param3);
cmd2.Parameters.Add(param4);
cmd2.ExecuteNonQuery();
}
connection.Close();
MessageBox.Show("Sucsess :)");
}