preventing duplicate row data entries - php

Question

I had created a database which named student with ID, name, mat_number, specialty, age, and gender, in a PHP application.
I do not want the name or mat_number be taken in more than once.
I have done the connection to my database in a different page and called it in the add student page.
This following codes is for a faculty database collection
<?php
if(isset($_POST['submit'])) {
$name = $_POST['name'];
$matNo = $_POST['mat_number'];
$age = $_POST['age'];
$specialty = $_POST['specialty'];
$gender = $_POST['gender'];
if(!empty($name) && !empty($matNo) && !empty($age) &&
!empty($specialty) && !empty($gender))
{
$sql = "INSERT INTO `student`(`name`, `UB_number`, `age`,
`sex`, `specialty`)
VALUES ('$name', '$matNo', '$age', '$gender', '$specialty')";
$conn->query($sql);
header("Location: index.php");
}
else{
echo "Error: Complete all records";
}
}
?>
I want to get an error message demanding for a change if the 2 fields already exist in the database.

Answer 1

first name to check in database if already exist the record.
if no record run sql insert command.
if(isset($_POST['submit'])) {
$name = $_POST['name'];
$matNo = $_POST['mat_number'];
$age = $_POST['age'];
$specialty = $_POST['specialty'];
$gender = $_POST['gender'];
$sql = "SELECT * FROM `student` WHERE name = "'.$name.'" and UB_number = '".$matNo."'";
$conn->query($sql);
$cnt = $conn->rowCount();
if($cnt == 0){
$sql = "INSERT INTO `student`
(`name`, `UB_number`, `age`,`sex`, `specialty`)
VALUES
('$name', '$matNo', '$age', '$gender', '$specialty')";
$conn->query($sql);
header("Location: index.php");
}else{
echo "Error: Complete all records";
}
}

Answer 2

If you would like to insert a new record to DB only if one doesn't exist which has the same name or mat_number then you first need to execute SELECT statement to see if it exists.
Using MySQLi:
<?php
include 'mysqli.php';
$conn = $mysqli;
if (isset($_POST['submit'])) {
$name = $_POST['name'];
$matNo = $_POST['mat_number'];
$age = $_POST['age'];
$specialty = $_POST['specialty'];
$gender = $_POST['gender'];
if ($name && $matNo && $age && $specialty && !$gender) {
$stmt = $conn->prepare('SELECT 1 FROM student WHERE name=? OR UB_number=?');
$stmt->bind_param('ss', $name, $matNo);
$stmt->execute();
$stmt->bind_result($exists);
$stmt->fetch();
if (!$exists) {
$stmt = $conn->prepare('INSERT INTO `student`(`name`, `UB_number`, `age`, `sex`, `specialty`) VALUES(?,?,?,?,?)');
$stmt->bind_param('sssss', $name, $matNo, $age, $gender, $specialty);
$stmt->execute();
exit(header("Location: index.php"));
} else {
echo 'A record with this name or material number already exists!';
}
} else {
echo "Error: Complete all records";
}
}
Using PDO:
<?php
include 'lib.php';
$conn = $pdo;
if (isset($_POST['submit'])) {
$name = $_POST['name'];
$matNo = $_POST['mat_number'];
$age = $_POST['age'];
$specialty = $_POST['specialty'];
$gender = $_POST['gender'];
if ($name && $matNo && $age && $specialty && !$gender) {
$stmt = $conn->prepare('SELECT 1 FROM student WHERE name=? OR UB_number=?');
$stmt->execute([$name, $matNo]);
$exists = $stmt->fetchColumn();
if (!$exists) {
$stmt = $conn->prepare('INSERT INTO `student`(`name`, `UB_number`, `age`, `sex`, `specialty`) VALUES(?,?,?,?,?)')
->execute([$name, $matNo, $age, $gender, $specialty]);
exit(header("Location: index.php"));
} else {
echo 'A record with this name or material number already exists!';
}
} else {
echo "Error: Complete all records";
}
}

Answer 3

hope this may be helpfull to you. In here I asume that you are not using any framework. But if you use a framework there are plenty of easy methods to do this.In here I have checked only name field. You should update code as you wants. Also it it better if you could validate your inputs before check. Like trim(). Thanks
<?php
if(isset($_POST['submit'])) {
$name = $_POST['name'];
$matNo = $_POST['mat_number'];
$age = $_POST['age'];
$specialty = $_POST['specialty'];
$gender = $_POST['gender'];
//after user click the submit button
$sql_Select_Stundets = "SELECT * FROM student WHERE name = '$name' ";
// query the sql with db connection
$result_sql_Select_Stundets = mysqli_query($conn,$sql_Select_Stundets);
//Now check the row count to verify the output if there is any match
$rowcount=mysqli_num_rows($result);
//Now write insert inside if condition
if( $rowcount >0 ) {
if(!empty($name) && !empty($matNo) && !empty($age) &&
!empty($specialty) && !empty($gender)) {
$sql = "INSERT INTO `student`(`name`, `UB_number`, `age`,
`sex`, `specialty`)
VALUES ('$name', '$matNo', '$age', '$gender', '$specialty')";
$conn->query($sql);
bheader("Location: index.php");
}else{
echo "Error: Complete all records";
}
}else{
echo "<script>
alert('sorry this name is already available');
</script>";
}
}
?>