Xml null field

There is no canonical answer, since XML fundamentally has no null concept. If you write handling, that means whatever you prefer. For tools that use XML Schema, xsi:nil is the way to go. It depends on how you validate your XML. If you use XML Schema validation, the correct way of representing null values is with the xsi:nil attribute.

The attribute mentioned in the other answer is a validation mechanism and not a representation of state. An element so labeled must be empty , but can carry attributes if permitted by the corresponding complex type. You use xsi:nil when your schema semantics indicate that an element has a default value, and that the default value should be used if the element isn't present.

I have to assume that there are smart people to whom the preceding sentence is not a self-evidently terrible idea, but it sounds like nine kinds of bad to me. Every XML format I've ever worked with represents null values by omitting the element. Or attribute, and good luck marking an attribute with xsi:nil.

When you are exchanging data, the role for which XML is commonly used, data sent to one recipient or for a given purpose may have content obscured that would be available to someone else who paid or had different authentication.

Knowing the reason why content was missing can be very important. Scientists also are concerned with why information is missing. For example, if it was dropped for quality reasons, they may want to see the original bad data. In many cases the purpose of a Null value is to serve for a data value that was not present in a previous version of your application.

If you use the 'no tag means null' representation you get automatic backward compatibility for reading your ReportMaster 1 xml file. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What is the correct way to represent null XML elements? Ask Question. Asked 12 years, 9 months ago. Active 4 months ago. Viewed k times. The XML for the examples above is contrived, so don't read too far into it. Community Bot 1 1 1 silver badge. Rob Hruska Rob Hruska k 28 28 gold badges silver badges bronze badges. Add a comment. Active Oldest Votes. A clarification: If you have a book xml element and one of the child elements is book:series you have several options when filling it out: Removing the element entirely - This can be done when you wish to indicate that series does not apply to this book or that book is not part of a series.

It is supposed to return NULL. The query above, however, does not return NULL, it returns This is all according to the documentation, so Microsoft isn't going to help us since they think this is to be the expected behavior. Martin Honnen led me on the way to the solution to my problem in his answer in this thread over at the MSDN forums. To get NULL returned by the. This way I could make the.

For the XML parser to understand that the xsi: prefix matches with the XMLSchema-instance name space we need to declare this namespace before we can execute the query. You can do this using the "with xmlnamespaces" clause. Here is the same example but now adapted with this new knowledge to retrieve a null value from the XML document:.

And the best thing is that this works identical for any type specified. Log in or register to rate. Join the discussion and add your comment. Missing data is a difficult and common problem to solve. In this article, Joe Celko explains several approaches to deleting or replacing missing data.

So here is the query;. Follow me on Twitter Follow me on FaceBook. May 4, May 4, April 27, April 27, April 22, April 22, I am very passionate about SQL Server.