检查数据是否在数据库中的功能

Question

我创建了一个函数来查找数据库中所有我的名字和姓氏，如果该数据已经存在，我只想输出，错误消息

我的问题是如何创建一个函数来检查数据是否已经存在？

这是我查找名字和姓氏的所有数据的功能。

function find_student_by_firstname($firstname){
  global $con;

  $safe_firstname = prep($firstname);

  $sql  = "SELECT * ";
  $sql .= "FROM studeprofile ";
  $sql .= "WHERE FirstName = '{$safe_firstname}' ";
  $sql .= "LIMIT 1";
  $student_set = mysqli_query($con, $sql);
  confirm_query($student_set);
  if($student = mysqli_fetch_assoc($student_set)){
    return $student;
  } else {
    return null;
  }
}

function find_student_by_lastname($lastname){
  global $con;

  $safe_lastname = prep($lastname);

  $sql  = "SELECT * ";
  $sql .= "FROM studeprofile ";
  $sql .= "WHERE LastName = '{$safe_lastname}' ";
  $sql .= "LIMIT 1";
  $student_set = mysqli_query($con, $sql);
  confirm_query($student_set);
  if($student = mysqli_fetch_assoc($student_set)){
    return $student;
  } else {
    return null;
  }
}

这是我当前检查数据是否已经存在的功能。

function match_fistname_lastname($lastname, $firstname){
  $student_firstname = find_student_by_firstname($lastname);
  if($student_firstname){
    find_student_by_lastname($lastname);
  } else {
    return false;
  }
}

Answer 1

如果用“数据已经存在”的意思是数据库中有一个与名和姓匹配的人，则不必执行两个查询。 像这样在mysql中使用and ：

function find_student($firstname, $lastname){
  global $con;

  $safe_firstname = prep($firstname);
  $safe_lastname = prep($lastname);

  $sql  = "SELECT * ";
  $sql .= "FROM studeprofile ";
  $sql .= "WHERE FirstName = '{$safe_firstname}' and LastName = '{$safe_lastname}' ";
  $sql .= "LIMIT 1";
  $student_set = mysqli_query($con, $sql);
  confirm_query($student_set);
  if($student = mysqli_fetch_assoc($student_set)){
    return $student;
  } else {
    return null;
  }
}