In this article, SQL Server provides us with a big library of system data types that define all types of data that can be used with SQL Server, from which we can choose the SQL Server data type that is suitable for the data we will store in that object. You can also define your own customized user-defined data type using a T-SQL script. SQL Server data types can be categorized into 7 main categories. When you will define SQL Server database tables, local variables, expressions, or parameters, you should specify what kind of data will be stored in those objects, such as text data, numbers, money, or dates. This attribute is called the SQL Server Data Type.
There are many examples in the below
declare @MNumber int set @MNumber = 123 select 'My number is ' + CAST(@MNumber as nvarchar(20))