If it's zero when it's set to zero and null when it hasn't been set to anything then you can differentiate between them. You may think you'll never want to differentiate between those two cases, but chances are you will. Here's another thread on the topic of nulls in DataSets, you may find it interesting. Regards, Sean. Friday, August 3, PM. OK - maybe I should have been more specific about where I'm having the problem. I'm not using a datareader - I'm using a dataset and dataadapter.
I'm making a form to view records, where I am manually reading and writing values back to the dataset, before updating to the database, with code such as: Code Snippet. Code Snippet. I had a look at thte C-Sharepcorner code - I tried this changing it a little, as it was coding for a datetime field, where I am doing it for nvarchar.
As far as I can see, it is saying something along the lines of "If the field is blank, then assign null to the field in the database". This seems to contradict what Sean Fowler said the first reply , in that nulls are important, as they tell you if the field is blank, or if it has been intentionally made blank by the user.
I tried to confirm this, and yes, it sets field which previously were non-null to null. Correct me if I'm wrong here, but that would defeat the purpose of having a null, as we no longer know if the field is null because it was never assigned a value, or if the user specifically wanted it to be empty. Saturday, August 4, AM. Depending on the controls you use it can all get a bit messy when you have the data maintained by a UI rather than being system-generated.
For example the standard DatePicker control can't handle nulls, so you end up with DateTime. MinValue getting put in the database, which is plain nasty. I use the Infragistics DatePicker instead as it can handle nulls. Their UltraTextEditor control can also handle null values. Then if it's unchecked the value is null, otherwise it's the value of the DatePicker. When using. 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. Replace null character in a string in sql Ask Question.
Asked 11 years, 11 months ago. Active 3 years, 5 months ago. Viewed 33k times. Improve this question. Add a comment. The following query will not compile because the fields that are referenced are missing from the SalesHistory table; however, it will work fine for showing the functionality of the COALESCE function. The COALESCE function is very useful in a join operation or in queries where you are comparing a single value from a list of possible fields to a single value.
Since NULL values are unknown, operations on them typically require some extra processing. As the list of values are returned, I am concatenating the literal string 'Sold' to the end of the Product value. On the record that returns the NULL value, this concatenation will not work correctly.
This example probably wouldn't be that useful in a production situation, but it does illustrate that you need to take special care when you encounter NULLs in string operations. You should also take care of calculations on numeric fields that allow NULL values. This is something to consider when you are defining your table structure and constraints. If you would like to contact Tim, please e-mail him at chapman.
TechRepublic's free SQL Server newsletter, delivered each Tuesday, contains hands-on tips that will help you become more adept with this powerful relational database management system. Are you sure that the DAL isn't inserting " " or ""?
Also, consider using more appropriate data-types for the columns e. And I'm not even going to ask why the "Date" column is an identity PK column.. Add a comment. Active Oldest Votes. Improve this answer. Anvesh Anvesh 5, 3 3 gold badges 40 40 silver badges 41 41 bronze badges.
For this I can use the default value. How can I check this? Sry Anu, I doesn't insert the value. I will Update the table with the Logout time
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