CREATE TABLE 上的 SQL 外键问题

Question

I used to a function FOREIGN KEY for link two tables together.

I'm straggling with that error: "errno: 150 "Foreign key constraint is incorrectly formed".

I could not find out where is problem. Please, I will thankful for any suggestions.

Thank, you for help.

This is my script written in PHP(see below).

<?php 

$servername = "localhost";
$username = "root";
$password = "";
$db = "myDB";

$conn = new mysqli($servername, $username, $password, $db);

if ($conn->connect_error) {
    die ( "Connection failed: " . $conn->connection_error);
}
echo "Connected successfully";

$sql = "CREATE DATABASE IF NOT EXISTS myDB";
if ($conn->query($sql) === TRUE) {
  echo "Database created successfully";
  } else {
      echo "Error creating database: " . $conn->error;
   }

$sql = "CREATE TABLE IF NOT EXISTS us_tAddress (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
country VARCHAR(100),
city VARCHAR(100),
zip VARCHAR(100), 
street VARCHAR(100),
created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP, 
updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
) ";

if ($conn->query($sql) === TRUE) {
    echo "Table us_tAddress created successfully";
    } else {
        echo "Error creating table: " . $conn->error;
    }


$sql = "CREATE TABLE IF NOT EXISTS us_tUser (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY, 
address_id INT (6),
first_name VARCHAR(100),
last_name VARCHAR(100),
position VARCHAR(100),
created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP, 
updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
FOREIGN KEY (address_id)  REFERENCES us_tAddress (id)
) ";

if ($conn->query($sql) === TRUE) {
    echo "Table us_tUser created successfully";
    } else {
    echo "Error creating table: " . $conn->error;
    }


$conn->close ();

?>

Answer 1

Your fields have different datatype.

Referenced column is id from us_tAddress with type id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY.
Referencing column is address_id from us_tUser with type INT (6).

You have to change type of id column in table us_tAddress to SIGNED or change datatype of field address_id in table us_tUser to UNSIGNED.