How to insert a column in a existing table in MySQL

Question

for($i=0;$i<=feof($getdata);$i++)
{
if (filter_var($data[$i][1], FILTER_VALIDATE_EMAIL)){
echo $data[$i][1];
$email=$data[$i][1];
$conn = mysqli_connect($dbhost,$dbuser,$dbpass, $dbname);
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}
$sql ="INSERT INTO promo_user (uid,name,email) VALUES (,'', '$email')";
mysqli_query($sql,$conn);
mysqli_close($conn);

I am using the above code but there is something wrong with it,whenever i run the code the echo is working fine but the content does go into sql table

Please help

Answer 1

User Alter table command.
Example -
ALTER TABLE table_name MODIFY column_name datatype

Answer 2

Add a column
ALTER TABLE name_of_the_table ADD column_name VARCHAR(size_of_the_column_name);

Answer 3

To add column at end of the table

ALTER TABLE table_name ADD column_name VARCHAR(10);

To insert a new column after a specific column, use this statement

ALTER TABLE table_name ADD new_column_name VARCHAR(10) AFTER existing_column_name;

If you want the new column to be first, use this statement:

ALTER TABLE table_name ADD column_name  VARCHAR(10) FIRST;