How to update the PRIMARY KEY/FOREIGN KEY in other related tables?

Question

walls

• wall_id (P)
• wall_name
• wall_views
• wall_downloads
• wall_thumbnail_path

(4, 'wall4', '125', '574', '../.../thumbnail_wall4.jpg')

types

• type_id
• type_name

('1', 'Desktop') ('2', 'Phone') ('3', 'Tablet')

wall_types

• wall_id (P) (F)
• type_id (P) (F)

(4, 1)

Above are the tables I have, what I want to do is automatically get the wall_id = 4 from walls tables and store it in wall_types table, same with the type_id from types table. How can this be done? what is the code (PHP code) or SQL statements to achieve this? thanks!

Note:

• wall_id in wall_types references wall_id in walls table.

• type_id in types references type_id in types table.

Answer 1

The query below inserts a new relation in your wall_types table, where '1' comes from user input (user selected 'Desktop'):

INSERT INTO wall_types (wall_id, type_id) VALUES (5,1);

If you want to do this right after you inserted a new 'wall' row where the id is (off course) unknown yet, you can use LAST_INSERT_ID(), this will contain the last inserted id, therefore you need to execute this query right after the 'wall' insert query:

INSERT INTO wall_types (wall_id, type_id) VALUES (LAST_INSERT_ID(),1);

Answer 2

If you want to do this "automatically" you can use Triggers to update the relashionship. The other way is remove the relationship in wall_types and re-create with the updated values.