The SQL XML data type is a data type that allows for the storage and manipulation of XML data within a relational database management system (RDBMS). XML, or Extensible Markup Language, is a format for representing and exchanging structured data on the web. By using the SQL XML data type, developers can store and retrieve XML data in a format that is easily accessible and searchable using SQL queries.
In SQL Server, the XML data type is a native data type that was introduced in SQL Server 2005. It can be used to store XML documents, XML fragments, or even XML namespaces. To declare a column as an XML data type, the XML keyword is used in the CREATE TABLE statement. For example:
CREATE TABLE myTable ( myXMLColumn XML )
Once the XML data is stored in the column, it can be manipulated using XML functions in SQL. Some of the commonly used XML functions in SQL Server include:
QUERY(): Returns a subset of the XML data that matches an XQuery expression.
VALUE(): Extracts a single value from an XML instance.
MODIFY(): Inserts, updates, or deletes XML data in the column.
The SQL XML data type is particularly useful for applications that require the storage and manipulation of complex and hierarchical data structures. It provides a convenient way to store and retrieve XML data in a relational database, without the need for a separate XML storage system. However, it is important to note that working with XML data can be more complex than working with other data types, and it requires a good understanding of the XML format and XML-specific SQL functions.