Despite being an interpreted language, Perl is hugely popular among programmers as a high-level, dynamic and general-purpose programming language. The text-handling capabilities of Perl make it easier for developers to generate SQL queries. But Perl5 uses Perl Database Interface (DBI) modules to implement database interfaces. The set of functions, conventions and variables defined by Perl DBI API specification provide a database-independent interface to the applications. Despite being independent of the original database used by the application, the interface is consistent and efficient. However, the programmers must consider common aspects of database programming with Perl.
Common Issues Associated with Database Programming with Perl
Each database is designed with features to support client/server protocols. The structure of Perl DBI is designed based on this principle. Normally, the database server waits for a request that can be made through a network, an internet socket or a file. While a request is being prepared, the DBI optimized it by checking its accuracy. Further, a single request can be reused wither with the same or different parameters. In case the database used by an application does not support the method of preparation, DBI simulates the process. Once the request is prepared successfully, client will ask the server for its execution. However, the server will not assume or identify the intentions of the end users. The server must be asked to execute the request and deliver the results.
Handles to Interact with Databases
DBI requires applications to interact with databases through three distinct object types or handles. The programmers have option to use database handles, driver handles and statement handles. The DBI creates handles for database connection by using the driver handles. The database handles can in turn be used to create handles for statements or individual database commands. Thus, the three distinct types of handles are related and inter-dependent. So the Perl programmers have to use the handles in the most appropriate order to interact and manipulate the databases.
While learning practical SQL, the learner has to associate it with a specific database. But the programmers rarely implement the database specific dialect while creating Perl applications. So the developers familiar with a specific SQL dialect often find it challenging to adopt a different database application. They, however, have option to address these common issues through standard ANSI SQL. But it is important for Perl programmers to understand the specific parts of SQL that need to be implemented to solve common problems related to database programming.
Despite being the official interface between Perl and databases, DBI require programmers to clearly define the requirements and know the design of the underlying database. So developers need to understand and use certain modules to avoid writing additional code. However, they can simplify complex database schemas by using DBI wrapper. Along with understanding various aspects of DBI wrapper clearly, the programmers need to learn how to overcome the limited commands supported by it.
Identifying the Client
Nowadays, users have option to access a web application on different devices. So the client/server applications have to deal differently with a web server and a database server. For the web server, the ultimate client is the person accessing the web application. But the web server process is always the client for the database server. The web server client is further required to provide the right username and password to access the password. Thus, the database server does not have any link with the end user or the device being used by him. So the Perl programmers have to write additional code to deliver the most relevant information to the end user.
While using Perl to develop web applications, programmers have option to use object-relational mappers to implement the DBI module. Some of these mappers can further generate SQL queries and handle data in a more transparent way.
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