Require field to be not null in sharepoint list

Question

I have several columns to input a number, the field is required with a default value of zero. This works fine when filling out the form, but once they save it then go back into the form the user can now put a blank value in that column and re-save the form and it doesn't reject it. I'm confused as to why validation only works during the first form fill and not after and how to avoid it.

I need to pull the data into an access database and I can't have blank values they cause all sorts of problems.

edit: Sorry I lied even though the fields are checked with Requires that this columns contain information it does allow a blank value even during first form fill, it hasn't always been that way. I did edit the form using InfoPath but even in InfoPath those fields are checked with "Cannot be blank".

Answer 1

Are you using any custom form with JavaScript validation, that is only on the form while creating new entry? But not while editing it? Best way to make that column/field mandatory is , go to list settings, click on column and chose radio button YES for required field.

Just saw your edit. Now we know that you are having Infopath form. Infopath form does accept blank spaces even when we say cannot be blank

If you are expecting users to enter number, you can have simple validation rule added there. may be field < 0, then show error message that only numbers greater than 0 are expected as an input.