Introduction to What is PL/SQL?
PL/SQL stands for Procedural Language extension to Structured Query Language. Before understanding PL/SQL one must know what SQL is and why is it used for? SQL stands for Structured Query Language and is used to handle data in Relational Databases (Databases in which data is stored in the form of rows and columns). SQL is used to write the queries and fire them against the database to insert, update, delete data.
PL/SQL
- PL/SQL is an extension of SQL that allows developers to combine the power of SQL with procedural statements. It was developed by Oracle Corporation in the early ’90s. It allows writing a piece of code including the SQL query in a block (which is the basic unit of it).
- It is a high standard and readable language so it is very easy to understand and learn. It can only be used with Oracle Database Systems and cannot be used as a standalone application like C, C++, Java, etc. It provides the facility to developers to use loops, conditions, object-oriented concepts and SQL like other database languages.
- Before PL/SQL, only one query is sent to the Oracle server at a time which increases the load and time. But through this, multiple SQL statements are grouped and sent in a single block or subprogram which increases the processing speed and decreases the traffic on Oracle Server.
Why should we use PL/SQL?
- Although PL/SQL at the end, executes and processes the SQL statements but consider a scenario of updating the salary record with the hike of 20% of all employees in the Employee table having 1000+ values, is it practical to write the update command 1000+ times and fire SQL query each time to update the records? For this PL/SQL came into the picture as through PL/SQL looping it can be done in 2 lines of code without any interruption in between
- Moreover, it is the fundamental of any web application to hide the implementation logic from the end-users. It is done through Interfaces in programming languages like Java, C++. Similarly, in Database intensive applications, the database is the main module and the SQL queries, tables are its implementation data.
- All these modules are hidden behind the PL/SQL interface. This way it maintains the correctness, maintainability, security, and abstraction for both the developers and end-users.
- It provides a special facility to work with the triggers (Triggers are special events that are fired when any specific, mentioned situation is met). This deals with various triggers like View level triggers, Database level triggers, Session level Triggers, and Table level triggers.
Advantages of PL/SQL
Below given are some of the advantages:
- It allows the users/developers to run multiple SQL statements at once by wrapping them in a block.
- It is compatible with SQL It allows us to use all the SQL statements, data manipulation, cursor handling, transaction statements in PL/SQL blocks. There is no need for conversion between the two of them.
- It is easy to maintain PL/SQL subprogram as only one copy is stored in the database server which can be accessed by all the clients and applications using it.
- It supports scalability by the access of centralized processing on database servers which allows multiple concurrent users to access it on a single node.
- It supports Portability, as the applications are written in PL/SQL, are portable to computer Operating System and hardware where Oracle database is present and working properly.
- It provides very easy and expressive syntax which is very easy to understand if someone is familiar with any programming languages.
- It allows users to define triggers that are fired automatically when a particular situation is met.
The Architecture of PL/SQL
This architecture consists of 3 components:
1. PL/SQL Block
It is the main part that contains all the code of PL/SQL. It is the actual input which contains the SQL statements and the instructions that will interact with the database
PL/SQL block mainly consists of 4 parts, i.e.
- DECLARE: This part of the code is optional. DECLARE section starts with the DECLARE keyword which contains all the variables, constants, and records that need to be declared before. It temporarily stores the data.
- BEGIN: It is the main section of the PL/SQL block and is mandatory. It contains all the logic written and tasks that need to be performed using the SQL queries through DDL and DML statements. It starts with the BEGIN keyword and ends with END
- EXCEPTION: This part of the block is optional and it handles the exception. It contains the code that needs to be executed when a runtime exception occurs. This section starts with an EXCEPTION keyword.
- END: This keyword specifies the end of PL/SQL This is mandatory to write in PL/SQL block as it indicates the end of the code.
2. PL/SQL Engine
This Engine is responsible for the actual processing of the PL/SQL statement. It compiles the code into bytecode and executes it. It separates the PL/SQL and SQL code and sends the actual SQL code to the database server where it interacts with the database. The remaining code is handled by the PL/SQL engine.
3. Database Server
It is the component where the data is stored and the SQL queries are sent by the PL/SQL Engine to interact with the data. It consists of SQL executor that parses and process further the SQL
How this Technology will help you in Career Growth?
- If we talk about any web application, 98% of the application deals with the data, either handling it, storing and manipulating it. To organize and handle huge amounts of data, there is a high demand for people in the market who have good knowledge of databases.
- As for the big applications, all the code cannot be kept in the application layer because it can degrade the overall performance of application when comes with sending a large number of requests to the database server at a time, so database professionals start implementing server-side coding which has wide scope in the market as it is implementing in all database-intensive applications and all this demands good knowledge of database languages like SQL, PL/SQL, Oracle, etc.
- Companies are ready to give great packages to DBAs as security and maintainability of data is their foremost priority.
Conclusion
The above discussion clearly shows the importance and the use of PL/SQL language in the field of database development and so on the application. SQL can help to deal with the data of database but PL/SQL helps to fire that SQL in a procedural way. If one needs to dive deep in the field of the database, good knowledge language is mandatory.
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