New Data Types in SQL Server 2008

With the advent of SQL Server 2008, comes the new set of data-types to make lives of developers more easy. They are as below:

Date and Time: Four new date and time data types have been added, making working with time much easier than it ever has in the past. They include: DATE, TIME, DATETIME2, and DATETIMEOFFSET.

Spatial: Two new spatial data types have been added--GEOMETRY and GEOGRAPHY--which you can use to natively store and manipulate location-based information, such as Global Positioning System (GPS) data.

HIERARCHYID: The HIERARCHYID data type is used to enable database applications to model hierarchical tree structures, such as the organization chart of a business.

FILESTREAM: FILESTREAM is not a data type as such, but is a variation of the VARBINARY(MAX) data type that allows unstructured data to be stored in the file system instead of inside the SQL Server database.

Of the above mentioned data-types, I feel that two of the data-types that would fall in the common usage of most of the applications would be Date & Time and HIERARCHYID.

Date & Time Data Types in SQL Server 2008

In SQL Server 2005 and earlier, SQL Server only offered two date and time data types: DATETIME and SMALLDATETIME. While they were useful in many cases, they had a lot of limitations, including:

• Both the date value and the time value are part of both of these data types, and you can’t choose to store one or the other. This often causes a lot of wasted storage (because you store data you don’t need or want); adds unwanted complexity to many queries because the data types often had to be converted to a different form to be useful; and often reduces performance because WHERE clauses with these data and time data types often had to include functions to convert them to a more useful form, preventing these queries from using indexes.
• They are not time-zone aware, which often requires extra coding for time-aware applications.
• Precision is only .333 seconds, which is often not granular enough for some applications.
• The range of supported dates is not adequate for some applications, and the range does not match the range of .NET CLR DATETIME data type, which requires additional conversion code.

To overcome these problems, SQL Server 2008 introduces four new date and time data types, which include:

• DATE: As you can imagine, the DATE data type only stores a date in the format of YYYY-MM-DD. It has a range of 0001-01-01 through 9999-12-32, which should be adequate for most business and scientific applications. The accuracy is 1 day, and it only takes 3 bytes to store the date.
• TIME: TIME is stored in the format: hh:mm:ss.nnnnnnn, with a range of 00:00:00.0000000 through 23:59:59:9999999 and is accurate to 100 nanoseconds. Storage depends on the precision and scale selected, and runs from 3 to 5 bytes.
• DATETIME2: DATETIME2 is very similar to the older DATETIME data type, but has a greater range and precision. The format is YYYY-MM-DD hh:mm:ss:nnnnnnnm with a range of 0001-01-01 00:00:00.0000000 through 9999-12-31 23:59:59.9999999, and an accuracy of 100 nanoseconds. Storage depends on the precision and scale selected, and runs from 6 to 8 bytes.
• DATETIMEOFFSET: DATETIMEOFFSET is similar to DATETIME2, but includes additional information to track the time zone. The format is YYYY-MM-DD hh:mm:ss[.nnnnnnn] [+-]hh:mm with a range of 0001-01-01 00:00:00.0000000 through 0001-01-01 00:00:00.0000000 through 9999-12-31 23:59:59.9999999 (in UTC), and an accuracy of 100 nanoseconds. Storage depends on the precision and scale selected, and runs from 8 to 10 bytes.

All of these new date and time data types work with SQL Server 2008 date and time functions, which have been enhanced in order to properly understand the new formats. In addition, some new date and time functions have been added to take advantage of the new capabilities of these four new data types.

HIERARCHYID Data Type in SQL Server 2008

While hierarchical tree structures are commonly used in many applications, SQL Server has not made it easy to represent and store them in relational tables. In SQL Server 2008, the HIERARCHYID data type has been added to help resolve this problem. It is designed to store values that represent the position of nodes of a hierarchal tree structure.

For example, the HIERARCHYID data type makes it easier to express these types of relationships without requiring multiple parent/child tables and complex joins.

• Organizational structures

• A set of tasks that make up a larger projects

• File systems (folders and their sub-folders)

• A classification of language terms

• A bill of materials to assemble or build a product

• A graphical representation of links between web pages

Unlike standard data types, the HIERARCHYID data type is a CLR user-defined type, and it exposes many methods that allow you to manipulate the date stored within it. For example, there are methods to get the current hierarchy level, get the previous level, get the next level, and many more.

In fact, the HIERARCHYID data type is only used to store hierarchical data; it does not automatically represent a hierarchical structure. It is the responsibility of the application to create and assign HIERARCHYID values in a way that represents the desired relationship. Think of a HIERARCHYID data type as a place to store positional nodes of a tree structure, not as a way to create the tree structure.