INSERT statement conflicted with the FOREIGN KEY constraint - SQL Server

Question

In your table dbo.Sup_Item_Cat, it has a foreign key reference to another table. The way a FK works is it cannot have a value in that column that is not also in the primary key column of the referenced table.

If you have SQL Server Management Studio, open it up and sp_help 'dbo.Sup_Item_Cat'. See which column that FK is on, and which column of which table it references. You're inserting some bad data.

Let me know if you need anything explained better!

I had this issue myself, regarding the error message that is received trying to populate a foreign key field. I ended up on this page in hopes of finding the answer. The checked answer on this page is indeed the correct one, unfortunately I feel that the answer is a bit incomplete for people not as familiar with SQL. I am fairly apt at writing code but SQL queries are new to me as well as building database tables.

Despite the checked answer being correct:

Mike M wrote-

"The way a FK works is it cannot have a value in that column that is not also in the primary key column of the referenced table."

What is missing from this answer is simply;

You must build the table containing the Primary Key first.

Another way to say it is;

You must Insert Data into the parent table, containing the Primary Key, before attempting to insert data into the child table containing the Foreign Key.

In short, many of the tutorials seem to be glazing over this fact so that if you were to try on your own and didn't realize there was an order of operations, then you would get this error. Naturally after adding the primary key data, your foreign key data in the child table must conform to the primary key field in the parent table, otherwise, you will still get this error.

If anyone read down this far. I hope this helped make the checked answer more clear. I know there are some of you who may feel that this sort of thing is pretty straight-forward and that opening a book would have answered this question before it was posted, but the truth is that not everyone learns in the same way.

You are trying to insert a record with a value in the foreign key column that doesn't exist in the foreign table.

For example: If you have Books and Authors tables where Books has a foreign key constraint on the Authors table and you try to insert a book record for which there is no author record.

You'll need to post your statement for more clarification. But...

That error means that the table you are inserting data into has a foreign key relationship with another table. Before data can be inserted, the value in the foreign key field must exist in the other table first.

The problem is not with client_id from what I can see. It looks more like the problem is with the 4th column, sup_item_cat_id

I would run

sp_helpconstraint sup_item

and pay attention to the constraint_keys column returned for the foreign key FK_Sup_Item_Sup_Item_Cat to confirm which column is the actual problem, but I am pretty sure it is not the one you are trying to fix. Besides '123123' looks suspect as well.

Something I found was that all the fields have to match EXACTLY.

For example, sending 'cat dog' is not the same as sending 'catdog'.

What I did to troubleshoot this was to script out the FK code from the table I was inserting data into, take note of the "Foreign Key" that had the constraints (in my case there were 2) and make sure those 2 fields values matched EXACTLY as they were in the table that was throwing the FK Constraint error.

Once I fixed the 2 fields giving my problems, life was good!

If you need a better explanation, let me know.