XQuery vs SQL

Confused whether to use XQuery or SQL? Or are you simply just wondering what actually the differences are between XQuery and SQL? You have come to the right place. Both XQuery and SQL are standard languages for retrieving information from XML. As a matter of fact, many XML storage vendors support both XQuery and SQL. Even so, you need to know how the two are different from each other in order to choose the right language that suits your needs best.

About XQuery
XQuery is famous partially because it is a W3C Recommendation. XQuery is a query (and also functional) programming language that is used to query and transform collections of data, either structured or unstructured, in the form of XML, text, or a vendor-specific extension for other data formats. It is developed by W3C’s XML Query working group, which works closely with W3C’s XSL working group.

About SQL
SQL actually stands for “Structured Query Language”. According to ANSI, SQL is the standard language for relational database management systems. SQL is used to update and retrieve data from a database. Common relational database management systems usually use SQL. Nevertheless, even though most database systems use SQL, many of them also have additional proprietary extensions that can only be used in their particular systems, in addition to the standard commands which can be used to perform almost everything already.

When to Use XQuery/SQL
SQL is a relational query language, so it is used only if all you are doing is querying relational databases. It is the way to go for most structured data. It is relatively simple, quick, effective, and efficient for handling relational sources. However, if you are querying XML, a combination of XML and relational databases, or unstructured data, XQuery should be the way to go. Why? XML’s logical structure involves hierarchy and sequence, which are exactly the two things that relational databases don’t do. Thus, SQL won’t be very suitable; XQuery, on the other hand, can do those things.

Developers that are already comfortable with XML development will find it very easy to adapt to XQuery. And XQuery gives strong performance on many XML tasks. Still, there are particular cases where SQL can be used for XML. Coding certain XML tasks in SQL may take extra effort, but this may be acceptable in some environments that are already comfortable with SQL’s maturity, strong API support, and domain knowledge for query optimization.

XQuerySQL
- A W3C Recommendation, query and functional programming language for structured and unstructured data- The ANSI standard language for relational database management systems
- Great for XML as well as a combination of XML and relational DBs- Great and efficient for querying relational databases
- Better performance on many XML tasks- May require extra effort for coding XML tasks

Conclusion
In general, SQL is better suited for handling structured data and relational databases. It is simple, quick, effective, and efficient. XQuery is the way to go for XML or a combination of XML and relational databases, due to the better performance on many XML tasks. But SQL for XML is still possible and acceptable in some environments, especially those that are already comfortable with SQL’s maturity, strong API support, and domain knowledge for query optimization.

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