Native queries in C++ and Java use SQL to provide concise and type-agnostic methods for querying databases. They offer benefits such as query hints and clean migration paths, and can overcome the shortcomings of string-based APIs. However, they are not necessarily portable and require a programmer to describe an SQL result set to map columns to entity properties.
Native queries are queries expressed using Structured Query Language (SQL) and are concise and type-agnostic methods of C++ and Java query expressions. Using native queries is beneficial in using specific features in databases, including query hints and some database-specific features. They are also useful for providing clean migration paths directly from applications that use SQL or Java Database Connectivity (JDBC). Native queries are used to provide results consisting of scalar values, entities, or both. These query types support the use of native SQL on a target database.
These types of queries can overcome the shortcomings of a string-based application programming interface (API). Queries of this type are used in an object database, where object persistence is a common task for programmers and a common feature of the database. Non-native queries, however, appear foreign in object-oriented programs because their expressions are simple strings and object graphs containing interleaved strings.
Native queries help alleviate the problems faced in databases by expressing a query within Java and C++. Queries can be written without an API or custom query language. Additionally, an integrated development environment (IDE) can help in reducing typos. Native queries would then be completely type safe and accessible by the refactoring features of an IDE. Finally, queries can be run, tested, and prototyped against collections of regular memory without a database backend.
Queries and their accompanying SQL are not necessarily portable to other databases. When many entities return from a particular native query, these same entities must be specified, as well as mapped, to column results in SQL statements in a metadata definition mapping software program. As a result, they can be used to map JDBC results via the persistent runtime into expected objects. The use of the name parameter is never defined for these query types, and portable applications can only use positional parameter binding for native SQL queries. Join support is limited to single value relationships.
To use native queries, a programmer must describe an SQL result set. The result set description helps a program like Entitymanager map columns to entity properties. Scalar results can also be defined and mixed with other entity results, resulting in an alias column being returned. Once the result sets are described, native queries can be run.
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