Question

I’m trying to INSERT into a table, but I get the error Cannot add or update a child row: a foreign key contraint fails.

And as the error says, I have a foreign key I’m trying to update.

Right now I’m using a simple INSERT like:

INSERT INTO tblTable1 (firstColumn, foreignKey) VALUES ('blabla', 1)

How can I insert this if foreignKey is the id of tblTable2?

Answer 1

You need to add the record to the parent table first, then the child table.

From MySQL documentation on foreign key constraints:

InnoDB rejects any INSERT or UPDATE operation that attempts to create
a foreign key value in a child table if there is no a matching
candidate key value in the parent table.

Here’s MySQL documentation of how to use foreign key constraints and examples.