Php 函数检查数据库中是否有数据

我创建了一个函数来查找数据库中的所有firstname和lastname如果数据已经存在，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firstname和lastname的所有数据的函数

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;
  }
}

这是我当前的功能，用于检查数据是否已经存在

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

如果您的意思是“数据已经存在”，即某人位于与firstname和lastname匹配的数据库中，则不必执行两个查询。 在mysql中使用

和
如下：

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;
  }
}

您知道SELECT查询的
和
运算符吗？只需选择名字匹配的条目
和姓氏匹配的条目即可。谢谢，您的建议有助于解决我的问题。