Phpmyadmin Won'T Save User_Id If Not Null

[konfused]

All the MySQL manuals that I own, or have borrowed, show a NOT NULL default for the user_id. In phpMyAdmin, if I enter NOT NULL for the user_id, an error message will prevent me from saving the table.  The error message reads #1067 Invalid default value for user_id. If I select None the table can be saved. The column user_id is auto_increment and the table works fine with None instead of NOT NULL. Would someone explain why this is so? . 

[Jonathon]

NOT NULL isn't a default. It's saying that the row cannot have a NULL value.

[konfused]

Thank you for replying so promptly Jonathon but as a newbie I don't understand what you say.

Why do all the manuals say "set the column as NOT NULL" but phpMyAdmin will only save when the column is set to None?

[Jonathon]

NOT NULL means a row cannot have a null value. In your case user_id means that it updates itself as you have set auto increment. Meaning you can leave that field blank and the DB will do the rest.

 

To clarify the default options in phpmyadmin are None, As defined, NULL, current timestamp.

 

You are looking at two different areas. The NOT NULL field is a check box and not an available option under DEFAULT

[konfused]

Many thanks Jonathon

 

As you say I was confused about the areas. I now leave the default fields as None and tick a NULL box where necessary and it all makes sense at last..