What does “Is Identity” column property mean in SQL Server?

Question

I am using SQL Server for the first time and I see that a column property is called Is Identity.

What does this mean?

What

Answer 1

It simply means the column uses the Identity(seed, increment) function to provide values for a primary key (usually). It is also known as "Autonumber". The second line below is an example:

CREATE TABLE Table (
TableID bigint IDENTITY(1,1) NOT NULL,
DateTimeStamp datetime NOT NULL DEFAULT (getdate()),
Data nvarchar(100) NOT NULL,
CONSTRAINT PK_Table PRIMARY KEY CLUSTERED 
(
    TableID ASC
)

It acts as a default value for the column that increments for each record. Note that you can also get the value inserted from SCOPE_IDENTITY(). Do not use @@IDENTITY as it is depreciated and can return the wrong result in the case of triggers or nested contexts.