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SQL vs PL/SQL - Key Difference

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SQL vs PL/SQL - Key Difference
Stechies

Data can be considered as facts or information that can be related to an object or a thing, such as a person’s height, weight, and student or employee identification number. In order to store and manage the data, we require a system that makes data manipulation and retrieval easy.

For this purpose, a relational database management system is used. A relational database is a collection of multiple data sets that are structured using tables, columns, and rows. In order to interact with these databases, you will require database manipulation languages. Two of the most commonly used database languages are SQL and PL/SQL.

SQL stands for Structured Query Language that you can use for adding, deleting, updating and manipulating data in a database. SQL has an extension called PL/SQL, that is actually a programming language. Users use the SQL statements within the PL/SQL code to develop programs.

To develop a better understanding of the basic concepts of these languages, let us take a closer look.

What is SQL?

SQL is the standard database programming language developed by IBM in 1970. Most relational databases support the SQL language. This is immensely helpful for Database Administrators, as they have to handle databases on a variety of platforms.

The relational database management system (RDBMS) lays down the foundation for all modern SQL servers such as MySQL, Microsoft Access, MS SQL Server and Oracle.
It has two basic parts – DDL and DML. DDL stands for Data Definition Language that is used for defining the schema or structure of the database.

The different SQL commands in DDL are:

  • Create
  • Alter
  • Drop
  • Comment
  • Truncate
  • Rename

DML stands for Data Manipulation Language. It is used for accessing and modifying the contents of the database. The different SQL commands in DML are:

  • Insert
  • Delete
  • Select
  • Update

Additionally, it has other methods to modify data in a relational database. They are:

TCL (Transaction Control Language)

These commands are used for checking the effect of other commands on the database:

  • Commit
  • Rollback
  • Savepoint

DCL (Data Control Language)

These commands are used to grant or take back privileges from database users:

  • Grant
  • Revoke

DQL (Data Query Language)

This command is used to pull data from databases based on certain conditions:

  • Select

Apart from database administration, SQL is used for writing data integration scripts and executing analytical queries for data analysis.

Whether you are a beginner or a professional, SQL is the first language you will come across when learning databases. As the learning curve is not very steep, picking up the basics won’t be tough.

Advantages of SQL

  • The language is extremely portable as it runs on desktops, laptops, smartphones and servers. The databases supported by SQL can be transported easily between different devices
  • Extensive programming knowledge is not required as the standard SQL statements can be used to manipulate the databases
  • It supports the client/ server architecture as it connects the front and back end systems
  • Using SQL, you can develop multiple views of the same database and execute data operations
  • It is easy to understand and learn as it contains mainly English statements for the queries. Moreover, the queries can e executed fast so it is ideal for beginners
  • It is open source and has a large community of developers and forums where you can look for support if needed

What is PL/SQL?

Developed in 1992 by Oracle, PL/SQL is a procedural database language. It is a combination of SQL and procedural statements. The PL/ SQL full form is Procedural
Language extensions to SQL. Its syntax is based on the programming languages of Pascal and ADA. It works by executing a block of code that has the following:

  • Triggers
  • Variables
  • Functions
  • Loops
  • Packages

It provides you with a programming environment that is independent of any operating system.

The entire code block is fed to the database engine at once so that code is processed faster. These blocks of code can be reused by nesting them under each other. Programmers are able to write effective code for manipulating databases as Pl/ SQL has for loops and if-else statements.

Its architecture consists of three components:

PL/SQL Block

This is the code block that is executed. It consists of three sections:

  • Declarative section for declarative statements
  • Execution section consisting of the processing statements
  • An exception handling section

It also contains the SQL instructions to communicate with the database server. The code block acts as the primary input in the architecture.

PL/SQL Engine

The PL / SQL Engine processes the code. Based on the input, the engine separates the SQL part and the PL/SQL statements. The PL/SQL statements are processed by the engine itself. The SQL part is sent to the database server for interacting with the database.

The engine can be installed in the application and the database server.

Database Server

The data is stored by the server. The interaction with the database takes place here using the SQL statements. The SQL executor parses the SQL statements and runs them.

Advantages of Pl/ SQL

  • Error handling is very efficient in PL/ SQL. When an exception or an error is raised, user-friendly messages are displayed and the executing block is stopped
  • As a block of code is sent for processing, network traffic is reduced and as a result, the database applications perform better
  • It benefits the programmer as variables can be declared within the code block and can be utilized when processing a query
  • The language is portable and applications developed through PL/ SQL can be run on any operating system
  • It offers features such as data hiding, encapsulation, and object-oriented programming. This will save you a lot of time during coding an application
  • Transaction performance of the applications can be enhanced as PL/ SQL lets you perform intermediate calculations without the Oracle engine

SQL vs PL/SQL

Let us now compare the two languages to understand them better.

Purpose

  • SQL works as a source of data stored in the form of tables, columns, and rows. This data can be retrieved, modified and displayed using SQL statements you provide.
  • In PL/ SQL, you can create programs that will display the contents of the database or table that is fetched using the SQL statements.

Execution

  • A particular query is executed at a time in SQL. These queries can be insert, update, delete or select statements.
  • But in PL/SQL an entire block of code is executed at once. You can execute multiple SQL statements using for loops, if-else constructs, and nested statements.

Type of language

  • SQL is a declarative language and a data-oriented language that is used to manipulate and analyze the data using SQL queries. It instructs what the database has to do with the data, but not how to do it.
  • On the other hand, PL/ SQL is a procedural language that is used to develop applications that tell the database what to do with the data. It is used to add business logic to back end systems.

Embedding

  • SQL statements can be inserted within the PL/SQL programs. But PL/ SQL code statements cannot be inserted in SQL code.

Uses

  • SQL is heavily used in organizations for handling large databases of customer, employee and client information. It is used to fetch data from these databases and develop analytical reports. Based on the data, the officials are able to take important business decisions.
  • SQL is also used for handling the back end of websites to store and process user information. Languages like PHP are used along with it.
  • PL/ SQL is used to provide the logic behind database applications. Languages like Java and PHP can be used with PL/ SQL to insert the logic statements. Additionally, it offers support for web applications and server pages.

Conclusion

We have understood that SQL and PL/ SQL have different uses and architecture. SQL is a declarative language that is used to give basic instructions to the database. But PL/ SQL is procedural and provides methods to extract data from a database.

SQL statements can be inserted in a block of PL/ SQL code but not the other way around. So, if your aim is to perform simple database manipulations like insert and update, SQL is perfect for you. But if you want to go ahead and develop applications that tweak the contents of a database, PL/ SQL is your best option.


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