If you need to add a new column in TSQL. You need to use the keyword function 'ALTER TABLE'. It is recommended you perform a check if the proposed column you want to add is not already existed in the database table otherwise you will receive an error message.
Let says we have a table called products with the following columns of information.
If we want to add a column named 'Description' with column type NVARCHAR(MAX) and we want to set the default value for a new column with an empty string and do not allow NULL value.
Here is the full TSQL query to add a new column in SQL Server.
IF NOT EXISTS(SELECT 1 FROM sys.columns WHERE Name = N'Description' AND Object_ID = Object_ID(N'dbo.Products')) BEGIN ALTER TABLE dbo.Products ADD Description NVARCHAR(MAX) DEFAULT '' NOT NULL END GO
Here is the final design of the table after we add the new column.