PostgreSQL XMLPARSE Example: Parsing and Manipulating XML Data

PostgreSQL XMLPARSE Example

Introduction

PostgreSQL is a powerful and feature-rich open-source relational database management system. One of its notable features is its support for XML data. In this article, we will explore how to use the XMLPARSE function in PostgreSQL.

XMLPARSE Function

The XMLPARSE function in PostgreSQL is used to parse an XML document and return a representation of it as an XML value. It takes a string containing the XML document as input and returns an XML value.

Example

Let’s consider an example where we have an XML document stored as a string in a table called «xml_data». The XML document represents a list of employees with their names and salaries.

Here is the XML document:
«`xml


John Doe
5000


Jane Smith
6000


«`

To parse this XML document using the XMLPARSE function, we can use the following SQL query:

«`sql
SELECT XMLPARSE(DOCUMENT xml_data) AS parsed_xml
FROM employees_table;
«`

This query retrieves the XML document from the «xml_data» column in the «employees_table» table and parses it using the XMLPARSE function. The result is stored in the «parsed_xml» column.

Working with the Parsed XML

Once the XML document is parsed, we can work with it using various XML functions and operators provided by PostgreSQL. For example, we can extract values from the parsed XML using XPath expressions.

Here is an example of how to extract the names of all employees from the parsed XML:

«`sql
SELECT xpath(‘/employees/employee/name/text()’, parsed_xml) AS employee_names
FROM parsed_xml_table;
«`

This query uses the XPATH function to extract the names of all employees from the parsed XML. The result is stored in the «employee_names» column.

Conclusion

The XMLPARSE function in PostgreSQL allows us to parse XML documents and work with them as XML values. This feature is useful when dealing with XML data in a relational database. By using the XMLPARSE function, we can easily extract information from XML documents and perform various operations on them.

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