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Handling Specialty Data
Lesson 24
Skills Matrix
Handling Special Data
• Managing an RDBMS has historically posed
special challenges for four specific
situations: handling XML data, hierarchical
data, spatial data and filestream data
storage options.
• SQL Serve now has built in data types and
processing support providing neat solutions
for these cases.
XML Data
• SQL Server 2005 added a new data type.
• This allows storage in a table—just like any
other data type—which can be indexed,
updated, modified or deleted—like any other
data type.
• Now, in addition to text or image binary large
objects (BLOBs), you can associate
structured or unstructured web-ready
content in your result set or report.
Hierarchical Data
• SQL Server 2008 added a new data type.
• The hierarchyid data type is a variable length,
system data type.
• Use hierarchyid to represent position in a
hierarchy.
• This lets you, for example, create organization
charts based on information in the database; or
create pedigree charts for all your race horses; or
track your entire family tree; or whatever you need
to display when data has positional relationships.
Spatial Data
• SQL Server 2008 added two new data types:
geometry and geography.
• Use these, for example, to display database
locations on a map or chart.
– Interface with Microsoft Virtual Earth and
display the location of your store in context
with all your store’s neighbors.
Filestream Data
• SQL Server 2008 added the ability to store
data on operating system files while at the
same time being able to manipulate the
data from SQL Server.
• Imagine being able to have customers play
one of hundreds of your “how to” videos on
demand from their web browsers; or provide
training videos for your employees managed
by SQL Server; or think of other possibilities
more applicable to your situation.
XML Data
• XML is an abbreviation for Extensible
Markup Language.
• XML has been evolving since 1997 and has
found widespread use as a standard for the
structure of data and for its transmission
across a variety of networks, most notably
the World Wide Web.
XML
• Used as:
– Metalanguage
– Markup Language
– Schema Definitions
– Extensible Stylesheet Language
XML Data
• When storing XML data in your database, you can store the
data as varchar or text data, you can decompose the data
in relational data, or you can store the data as a native XML
data type:
– When storing XML as varchar or text data, you will lose
most of its representation.
– You can shred (reformat) the XML document into
relational data and use a FOR XML clause with the
SELECT statement to retrieve an XML structure from the
relational data you store in the database.
– Since SQL Server supports XML as a true data type, you
can now benefit from that by storing XML natively inside
the database.
Using XML Data Type
• You can use the XML data type in many
ways; it is comparable to using any other
SQL Server data type.
• Of course, you can also use XML data types
in stored procedures as parameters and
many other options.
• SQL Server is flexible in the way you work
with the XML data; you have the ability to
store both typed XML and untyped XML in
the database.
Untyped XML
• When using untyped XML, you can store XML
in the database in any form, as long as it is
well-formed XML.
• This means that upon defining an XML
column and inserting or assigning a value to
the XML column, a check will occur to see
whether the data you are about to insert
matches the XML standard, without
validating it against an XML schema.
Typed XML
• If you want to validate XML with an XML schema,
you can specify an XML schema validation when
creating or defining the XML data type.
• You do this by referring to the XML schema, which
you initially need to store and catalog in the SQL
database.
• XML that is validated by an XML schema is called
typed XML.
• An XML schema validation is like putting a check
constraint on a scalar data type, since it performs a
check on the values you provide.
Typed XML
• When an XML data type is assigned to a Schema
collection, you will not be able to insert any columns
that don’t match the schema definition.
• To use XML Schema collections in the database and
associate them with variables and columns of the XML
data type, SQL Server uses the CREATE XML SCHEMA.
• When an XML data type is assigned to a Schema
collection, you will not be able to insert any columns
that don’t match the schema definition.
• Once the schema is defined, you can use it and refer to
it in a CREATE TABLE or even a DECLARE XML
statement.
Querying XML Data
• Because of the hierarchical structure inside XML data, you can
use query methods to retrieve information and search for data
in an XML data type.
• The XML methods you can use to retrieve data from an XML
data type are as follows:
– Query method: Returns a fragment of untyped XML.
– Value method: Returns XML data as a scalar data type.
– Exists method: Checks whether a certain node exists in the
XML data.
– Modify method: Changes the contents of an XML
document.
– Nodes method: Returns a single column rowset of nodes
from the XML column.
Decomposing XML Data
• As database administrator, you can benefit
from using XML in combination with the
EVENTDATA( ) function.
• If you have to write a trigger every time you
want to use the Eventdata collection, and in
that trigger decompose your XML data into a
relational format to store it inside a log table,
you would be wasting a lot of work rewriting
or copying the code data that decomposes
the Eventdata results in relational data.
Creating XML Indexes
• The XML column in its native data type
provides great capabilities in terms of
retrieving data from within the XML column
using various query methods.
• To support the querying of XML data, you
can create indexes on these columns.
• The start of an XML index is a primary XML
index, and all other XML indexes will depend
on the primary index.
Creating XML Indexes
• The start of an XML index is a primary XML index,
and all other XML indexes will depend on the
primary index.
• You have the ability to create the following XML
indexes to support optimized XML querying:
– Primary XML index
– Path XML index
– Value XML index
– Property XML index
External File Management
• SQL Server introduced the FILESTREAM feature
with the release of SQL Server 2008.
– It works something like a hybrid of your traditional
choices.
• Now you can store your files external to SQL Server
while SQL Server continues to maintain
transactional consistency.
• FILESTREAM also enables integration with
Transact-SQL and manageability features: ACID,
triggers, full-text search, backup and restore,
security, database console checks and replication.
Summary
• In this lesson, you learned about the XML data type,
which is a new and native data type supported in SQL
Server.
• Using and storing XML data in SQL Server can be easy
or complex, but it is important that you understand the
benefits of using the XML data type.
• You also learned how SQL Server works with XML and
how you can decompose XML into relational data.
• However, these are just basic components of the XML
data type and its associated methods.
Summary
• To query XML data, you learned different methods
to use.
• The nodes and value methods can convert XML
data into relational data and, therefore, are
probably the most commonly used methods.
• SQL Server supports two types of XML: typed and
untyped.
• When using typed XML, you first need to catalog
the XML Schema inside SQL Server using a
CREATE XML SCHEMA COLLECTION statement.
Summary
• You also learned the basics of hierarchical,
spatial and external file management.
• Hierarchical stores information about related
data sets; spatial stores geometric or
geographic descriptors that can be used with
other display technologies to create a visual
result; and external file management can
stream data from your database to desiring
users.
Summary for Certification Examination
• Be able to identify the data structure. Understand
when to use XML and when another data type is
preferable or usable.
• Know how to retrieve XML data.
– To retrieve XML data, you can use several
methods.
– To be able to work with XML data, it is important
to know the query, exist, nodes, value, and
modify methods.
– You need to fully understand how to decompose
to XML, as well as how to convert it.
Summary for Certification Examination
• Know how to modify XML data. XML data can be
modified in the XML column using the modify method,
and you don’t need to shred out and update the entire
XML data in order to replace, insert, or even delete
data in an XML column.
• Understand how to convert between XML data and
relational data.
– Since the XML data type is near the highest in the
data type precedence hierarchy, you will have
conversion from and to the XML data type.
– It is important to know how to use the CAST and
CONVERT functions to support the XML data type.
Summary for Certification Examination
• Know how to create an XML index. When optimizing XML
querying, you can create multiple indexes, which are the
primary starting points for your XML optimization.
• To support the various types of XML queries, you will create
secondary indexes.
• Know how to load an XML schema. SQL Server stores typed
or untyped XML.
– When storing typed XML, you first will need to load an
XML schema in the database before you can use it, and
have schema validation in variables, columns, and
expressions.
– It is important to be familiar with this syntax.
Summary for Certification Examination
• No certification requirements currently exist
on Microsoft's Learning web page for
hierarchical, spatial or external file
management although these are important
new features of SQL Server 2008.