如何从具有主键自动增量的表中向具有外键的表中插入数据？

Question

I have 4 mySQL tables with the following entries:

user
-user_id PK,AI
-user_name
-user_mobil
-user_passw
-user_email

bookingdetails
-booking_id PK,AI
-booking_date
-booking_time
-person_number

booking
-booking-_id FK
-restaurant_id CK
-user_id CK

restaurant
-restaurant_id PK
-restaurant_name
-restaurant_address
-restaurant_description

I would like to make a booking, I insert all the bookingdetails data, which gives me a AI booking_id, and after I would like to make my booking table and insert the restaurant_id and the user_id With the same booking_id which was given by the bookingdetails table.

I made the following code for achieve that in php on a localserver:

 $booking_date=$_POST["booking_date"];
 $booking_time=$_POST["booking_time"];
 $number_of_place=$_POST["number_of_place"];
 $customer_id=$_POST["customer_id"];
 $restaurant_id=$_POST["restaurant_id"];
 $res;


 $sql_query = "INSERT INTO bookingdetails(booking_date, booking_time, number_of_place) VALUES ('$booking_date','$booking_time', '$number_of_place')";
 $sql_query2 = "INSERT INTO `booking`(`booking_id`, `customer_id`, `restaurant_id`) SELECT booking_id, '$customer_id', '$restaurant_id' FROM   bookingdetails ORDER BY booking_id DESC LIMIT 1 ;";


 if(mysqli_query($con,$sql_query))
 {


 }
 else
 {


 }



 if(mysqli_query($con,$sql_query2))
 {


 }
 else
 {


 } 



 ?>

Is that a legit solution on a server which joining to an Android app? Is there any case, that i don't get the good id on the second query? What would be a better solution?

Answer 1

Answer given in comment by @Mark Ng

Use last insert id, criteria is that your pk has to be AI.

The mysqli_insert_id() function returns the id (generated with AUTO_INCREMENT) used in the last query.

Source: w3schools.com/php/php_mysql_insert_lastid.asp

To elaborate

you have to execute the query from which you need the last inserted id, then you can access that by using

 $last_id = $conn->insert_id;

which in turn you can use for your following query.

Note:

I see you use a query to use the results for your insert query, but your syntax is incorrect (your missing values )