How to Set a Column Value to Null in SQL Server Management Studio

How do I set a column value to NULL in SQL Server Management Studio?

If you've opened a table and you want to clear an existing value to NULL, click on the value, and press Ctrl+0.

How to enter 'NULL' into SSMS cell?

Just enter 'NULL' (with single quote mark) into cell, SSMS will trim leading and ending single quote mark and save it as string 'NULL'.

Without single quote mark, SSMS will treat input as NULL.

Altering a column to be nullable

Assuming SQL Server (based on your previous questions):

ALTER TABLE Merchant_Pending_Functions ALTER COLUMN NumberOfLocations INT NULL

Replace INT with your actual datatype.

Replacing NULL with 0 in a SQL server query

When you want to replace a possibly null column with something else, use IsNull.

SELECT ISNULL(myColumn, 0 ) FROM myTable

This will put a 0 in myColumn if it is null in the first place.

SQL Server: why is it possible to set default NULL value on NON-NULLable column?

To reinforce Larnu's comment: By setting a default of null (or simply accepting the system default), you are making it explicit that failing to insert a domain value will cause an error. Suppose you set a default of 1. Then I could insert a row without specifying that column as part of the insert list, or providing any value for the column. That might lead to undesired or unpredicted behaviour. The not null with a null default says "if you want to create a member of this set, this attribute must be defined by you before you can do so"

Fiddle example from Aaron Bertrand

In the comments you also made the comparison with a C# bool, but a C# bool literally cannot be null, which is different from a SQL bit, which can be. In order to make the comparison you would have to compare with a C# bool?, whose default value is null.

C c = new();
if (c.b is null) Console.WriteLine("it is null"); // prints "it is null"

internal class C
{
   public bool? b;
}

Edit: From the comments it seems like this argument is a bit abstract, so I'll try to make it clearer using a different example, and a different datatype.

Suppose I have the idea of a "Customer" in my domain. A Customer has a name attribute. In my model (based on my business requirements) it wouldn't make any sense to be able to create a Customer without a name.

In such a scenario, I specify that the name column is therefore not null.

But what should I specify as a default? Clearly it doesn't really make any sense to specify a default value for name. If we set the default to "Bob", we'd really just be lying to ourselves. If we set the default to an empty string we've now shot ourselves in the foot, because all we've done is circumvented the business rule, we haven't actually created any meaningful Customers if those customers have no name.

So in my model I want to specify that in order to create a Customer, you have to supply a legitimate value for name. I therefore make the column not null and make the deliberate choice to not supply an acceptable default.

You could, of course, still explicitly populate the name column with an emptry string when you come along an insert data... but now, that's on you, as the person creating the data. The model has specified what it expects, and you have to be quite deliberate about circumventing that. If we had given the column a meaningless default, people could flout the business rule "accidentally", as it were, without even realising it.

How do I set the Allow Nulls property in table designer of SSMS to be always false?

If you are fine with manipulating the registry key, here is an option to force the SSMS to always assign the value false to Allow Null property.

NOTE: Please be careful while altering registry keys.

1. Type regedit in the Windows Start --> Run command to open the Registry Editor.

2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Microsoft SQL Server\100\Tools\Shell\DataProject You might need to change the SQL Server version accordingly. I am using SQL Server 2008 R2 Express and hence the version 100.

3. Under the above mentioned registry path, look for the key name SSVDefaultAllowNull.

4. Right-click on the key and select Modify option. Change the value from 1 to 0. Default value is 1, which represents True.

5. If you are already running SQL Server Management Studio, restart it. Thanks to @Andriy M for pointing out this step.

Hope that helps.

Not equal != operator on NULL

<> is Standard SQL-92; != is its equivalent. Both evaluate for values, which NULL is not -- NULL is a placeholder to say there is the absence of a value.

Which is why you can only use IS NULL/IS NOT NULL as predicates for such situations.

This behavior is not specific to SQL Server. All standards-compliant SQL dialects work the same way.

Note: To compare if your value is not null, you use IS NOT NULL, while to compare with not null value, you use <> 'YOUR_VALUE'. I can't say if my value equals or not equals to NULL, but I can say if my value is NULL or NOT NULL. I can compare if my value is something other than NULL.

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