同时插入多个外键

Question

I have a form that gathers user input regarding a property they showed (a realtor showing to potential business leasees).

Upon submitting the form, I insert the data into three tables: Showing , Business , and Contact . This form allows for the creation of new Businesses and new Contacts , while also creating a new Showing record.

I can insert the information into either my Business table and my Contacts table fine with an auto-incrementing primary key .

How do I insert the primary key from Contacts as a foreign key in Business when they are both submitted at the same time?

Should I have a values table which I select from for both the primary key and the foreign key ? What are the best practices around this?

Additionally, I would like the insert the primary keys from both Business and Contacts as foreign keys in my Showing table. I currently have a BusinessID as foreign key within Contacts but maybe Contacts should stand alone so that I can Insert it first and then just select for the subsequent foreign keys ?

Finally I should note that for a database I am using phpMyAdmin and inserting via SQL within a .php page.

Answer 1

To retrieve the value assigned to an AUTO_INCREMENT column when a row is inserted, MySQL provides a last_insert_id() function.

Immediately following a successful insert that assigned a value to an AUTO_INCREMENT column, in the same session, before any other SQL statements are issued, you can run a query:

SELECT LAST_INSERT_ID()

The value returned from that can be used in a subsequent INSERT. In your scenario, that value can be supplied as the value for the foreign key column.