Write a query to delete the row from the 'userdetails' table where the userId is 104.

Sure, here is the SQL query to delete a row from the 'userdetails' table where the userId is 104:

DELETE FROM userdetails
WHERE userId = 104;

Here's a step-by-step breakdown:

1. DELETE FROM userdetails: This part of the query specifies that you want to delete from the 'userdetails' table.

2. WHERE userId = 104;: This is the condition that selects the row to be deleted. It says to delete the row where the 'userId' is 104.

Please note that running this query will permanently delete this row from your table. If you want to be able to recover the data, consider backing it up before running the query.