Difference between SQL and PL/SQL – A Comparison Guide
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In today’s world, data is the key to a company’s growth in every domain, whether it is artificial intelligence, data science, or machine learning. SQL (Structured Query Language) and PL/SQL (Procedural Language/SQL) play crucial roles in data management. There lies a significant difference in their purpose, structure, and usage though both are meant for interaction with databases. When it comes to handling errors, communicating with databases, and carrying out operations, PLSQL and SQL differ from one another.
This comprehensive guide will discuss the differences between SQL and PL/SQL, including the features, advantages, disadvantages, and real-world applications. By the end of it, you will have a good understanding of both languages and their appropriate roles within Database Management Systems (DBMS).
Before discussing the major differences, we must understand the objectives and background of SQL and PL/SQL since both are essential components of Oracle Database and other databases as well. SQL stands for Structured Query Language and is the standard language for querying and manipulating data within a relational database. PL/SQL, on the other hand, is an acronym for Procedural Language/Structured Query Language. It is a procedural extension to SQL and is designed to be seamlessly integrated into Oracle’s SQL query and data manipulation facilities.
What is SQL?
SQL is a programming language that doesn’t follow a specific procedure, and it’s used to work with relational databases. It was developed by IBM in the 1970s and is currently supported by nearly all relational database systems. It is highly efficient for working with structured data, making it the go-to language for database interaction. Accessing, managing, and obtaining data from any database is simple when SQL is used. Data manipulation and querying are the main purposes of SQL. It makes data handling easier by enabling users to add, edit, remove, and retrieve data within databases.
SQL provides a higher level of abstraction than procedural languages and is far more portable and upgradeable. SQL Additionally, it can be used to create and alter the tables, indexes, and database constraints that make up a database’s schema (structure).
Syntax:
SELECT column1, column2
FROM table_name
WHERE condition;
Example:
SELECT emp_id, f_name, l_name
FROM emp
WHERE dept_id = 30;
In this example, we are retrieving the employee details from the “emp” table where the department ID is 30.
Types of SQL Statements
SQL is divided into several categories depending on its purpose:
1. Data Query Language (DQL): A DQL statement is used to query data from the database.
Example: SELECT statement.
2. Data Manipulation Language (DML): A DML statement is used to manipulate existing data within the tables.
Example: INSERT, UPDATE, DELETE.
3. Data Definition Language (DDL): A DDL statement is used to define or modify the structure of database objects like tables, views, etc.
Example: CREATE, ALTER, DROP.
4. Data Control Language (DCL): A DCL statement is used to control access to data within the database.
Example: GRANT, REVOKE.
5. Transaction Control Language (TCL): A TCL statement is used to manage transactions in the database.
Example: COMMIT, ROLLBACK.
Features of SQL
Below are some key features of SQL:
Standardised: SQL is standardised by ANSI and is a widely used database language.
Declarative language: SQL is a declarative language, which means that instead of explaining how to accomplish a task, you can declare what you want to accomplish (i.e., query data).
Portability: With very few changes, SQL queries can be executed on a variety of database systems, allowing for smooth cross-platform data administration.
Data control: Using Data Control Language (DCL) statements, SQL can also regulate data access.
Security: Strong security and administration features, including transaction management and user access control, are offered by SQL.
Data manipulation: SQL allows to query and manipulate data.
Data definition: SQL can use Data Definition Language (DDL) statements to describe and alter the structure of the data.
Advantages of SQL
Simplicity and Ease of Use: The beauty of SQL is its subtleness in that it is easy even for newcomers to master. After basic training, it is possible to retrieve information from the database using queries without knowledge of any programming.
Standardised Language: Because it is an American National Standard Institute format, it is a formulated structure that is the same in every database system made with such codes as Mysql, PostgreSQL, and Sql server.
Declarative Nature: In SQL it is possible to state what the user wants retrieved but does not say how to go about it. This assists a lot in speeding up the writing of queries.
Portability: The SQL language is very portable in that very few changes are required to run an SQL language on various databases.
Efficient Data Handling: Due to the inclusion of indexing in SQL, this improves data access speed as the size of data increases, therefore, efficient database operations are recommended.
Powerful Data Manipulation: The task of adding, modifying or even deleting data from a data-based page is made simple using SQL.
Disadvantages of SQL
Lack of Procedural Logic: Lack of procedural language loops, conditional statements, and other such constructs limit the extent to which SQL could be used for logic involved in programming.
Partial Control: Due to the underlying business rules, SQL programmers are not in total control of the database.
Operating Cost: Some programmers find it challenging to access some SQL versions due to their high operating costs.
Limited Error Handling: Real situations on the other hand showed so many areas of limitations as to how queries were programmed particularly SQL with regards to errors.
Scalability Issues: It cannot be emphasised enough that SQL language is not a suitable tool for handling the managing of complex business logic since such attempts lead to large, tedious, and even unmanageable queries.
Overhead for Complicated Operations: Where more than two queries are required for the operation, it entails many round trips to the database making SQL costly.
Less Control Over Execution: There are some limitations in SQL in that the execution flow is not controlled at a patch level which makes implementation of very elaborate business logic templates difficult.
What is PL/SQL?
Procedural Language for SQL, or PL/SQL, is an addition to SQL that was created by Oracle Corporation. Procedural languages like PL/SQL are made especially to support SQL statements in their syntax. It makes it possible to perform more sophisticated and important operations on the Oracle database by using the declarative qualities of SQL with the procedural characteristics present in programming languages. It allows developers to write complex programs using procedural programming features such as loops, conditions, and variables, making it a more powerful tool for managing databases. It also processes data at a very high speed. The primary reason for the popularity of the PL/SQL language is its ability to manage significant errors.
In the Oracle database context, PL/SQL is mostly used to write and run procedures, functions, triggers, and packages. The procedural language is incredibly strong and allows procedural constructs to be extended to SQL statements. The Oracle Database server compiles and stores PL/SQL program units inside the database. Additionally, for maximum efficiency, SQL and PL/SQL execute within the same server process at run-time. PL/SQL provides the best stability, security, and mobility by inheriting all of its features from the Oracle Database.
The structure of a PL/SQL block consists of only four parts: DECLARE, BEGIN, EXCEPTION, and END.
Syntax:
DECLARE
variable_name data_type;
BEGIN
-- SQL statements
-- Control structures
-- Exception handling
END;
Example:
DECLARE
CURSOR emp_cursor IS
SELECT emp_id, f_name
FROM emp
WHERE dept_id = 30;
BEGIN
FOR emp IN emp_cursor LOOP
DBMS_OUTPUT.PUT_LINE('Processing employee: ' || emp.f_name);
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE('No employees found.');
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('An error occurred: ' || SQLERRM);
END;
In this example, we are processing all employees in Department 30, and printing their names.
Features of PL/SQL
Below are some key features of PL/SQL:
Procedural: As PL/SQL is procedural, it allows you to specify the logic behind how operations should be carried out, in contrast to declarative SQL.
Block of Code: PL/SQL programs are composed of declarative, executable, and exception-handling code blocks.
Efficiency: It also allows SQL statements to be executed in batches, which lowers network traffic and boosts performance.
Integration with SQL: PL/SQL and SQL are completely integrated, enabling programmers to run SQL statements inside of PL/SQL blocks.
Portability: PL/SQL programs can be run on any platform or operating system and are compatible with Oracle databases.
Functions and Procedures: User-defined functions and procedures for reusable code are supported by PL/SQL.
Control structures: Loops, conditions, and exceptions are examples of procedural control structures that PL/SQL can handle.
Error Handling: Strong error-handling methods with exceptions are provided by PL/SQL.
Advantages of PL/SQL
Use of Procedure Programming Logic: When including the constructs in PL/SQL, these can include procedure programming features such as loops, conditionals, and functions thereby allowing for complex programming logic.
Error Management System: PL/SQL Error Management System is very relational, capturing the exception and solving the errors.
Improved Performance for Complex Operations: PL/SQL combines numerous SQL statements into a single unit to minimise the network load thus improving the performance of such operations.
Modularity: Procedural-oriented language PL/SQL, gives the opportunity to code reusable parts as procedures, functions, and packages thereby enhancing the structuring and maintenance of the code.
Business Logic Control: It is possible in PL/SQL for the developer to invoke a commit or rollback anywhere in the logic without any errors occurring.
Scalability: Scalability is improved by its stored subprograms, which centralise application processing on the database server.
Disadvantages of PL/SQL
Learning Curve: As compared to SQL, PL/SQL is of higher difficulty as it comes with procedures, which tend to take time to learn.
Oracle-Specific: Since PL/SQL is associated with Oracle systems, this could be a disadvantage for projects that require the use of multiple database systems.
Limited I/O features: I/O operations in PL/SQL which involve reading or writing files and reading or writing to user interfaces can hardly be considered enough
Overhead for Simple tasks: PL/SQL, however, is often not appropriate, especially in the performance of simple tasks and queries such as creating functional or data manipulation statements where straight SQL would have sufficed.
Performance Considerations: PL/SQL has an added advantage in that it seeks to reduce the effect of multiple executions of SQL against a database at the time of performing a database using PL/SQL. Poorly architected PL/SQL codes can lead to SQL bottlenecks.
Complex syntax: There are moments when programmers have trouble applying PL/SQL because of the bateau of its complexity and irregular structure.
Development Environment Dependency: In addition, PL/SQL is seldom productive when it comes to developing without proper and applying Oracle development tools.
PL/SQL supports modular programming i.e., using procedures and functions.
Integration
SQL can be used independently i.e., without PL/SQL.
This is fully integrated with SQL and supports executing SQL within PL/SQL blocks.
Security
Basic security through roles and permissions, setting up of passwords, etc.
It provides enhanced security through definer and invoker rights.
Environment
It can be executed in any SQL environment.
It requires an Oracle database environment.
Use Cases
Data querying, reporting, CRUD operations.
Complex business logic, triggers, and stored procedures.
Return Types
SQL does not have any return type or values.
PL/SQL can return values from functions.
Learning Type
SQL is very easy to learn.
PL/SQL requires prerequisites as SQL and has a steeper learning curve.
Deployment
SQL statements are deployed in scripts or applications.
PL/SQL programs are deployed in the database as stored procedures.
Processing Speed
For large amounts of data, SQL does not provide fast processing times.
High processing speed for large amounts of data is provided by PL/SQL.
Applications of SQL and PL/SQL
Here are the different applications of SQL and PL/SQL used in managing the data in database management systems by providing various features including security, integrity, efficiency, etc.
Applications of SQL
Data Retrieval: SQL is used in seeking out information from databases for leadership reports and declarations via the use of SELECT statements on the data tables.
Data Manipulation: Adding records data in the database or changing some details and removing some of the data from the database using the commands of INSERT, UPDATE, and DELETE.
Database Management: Building relations including foreign keys (like primary, and foreign keys) and creating new records to database objects such as tables, indexes, and views, using the CREATE, ALTER, and DROP commands.
Data Science and Machine Learning: Adopting the concepts of SQL is an added advantage for data scientists and machine Learning engineers. This is mostly because they work with big amounts of data.
Data Analysis: This includes doing complex queries e.g. joins, scalar, and group by subqueries to help in drawing insights from the data.
Web Development: In web development, web databases are queried and SQL is one of the means that is used to query them. It is very important since it helps in the creation of web applications that are dynamic that use data, store data, retrieve it, and process it hence presenting a better way for the end users to interact with applications.
Reporting: Data in preparation for reports or dashboards is accessed or retrieved typically combining with business intelligence.
Business Intelligence (BI): Business Intelligence is a process that focuses on extracting valuable insights from available data through the use of SQL. The users can apply the use of SQL for decision support, analytical reporting, and market analysis.
Applications of PL/SQL
Stored Procedures and Functions: PL/SQL helps in developing the stored procedures and functions that contain business logic in a reusable manner for better code structure and maintenance.
Batch Processing: Normal reporting devising which requires several SQL operators is done by carrying out all the commands in one single PL/SQL block.
Customer Relationship Management (CRM): Specific implementation of business logic is also done in PL/SQL in CRM systems, as well as application integration with databases.
Triggers: Creating procedures for database tables automating a particular activity that is triggered by an event and could involve changing some data.
Complex Business Logic: Permitting or carrying out complicated business rules that need many activities and conditions to be completed by the database.
Enterprise Resource Planning (ERP): Most provisions of PL/SQL are utilised in application development, integration, and customization of business solutions in Oracle E-Business Suite ERP systems e.g. Sigma.
Data Validation: Ensuring the validation and integrity of data before inserting or updating any record is executed using PL SQL.
Business Intelligence: A lot of data processed using PL SQL is used in generating reports and various other analytical needs, especially within BI.
Conclusion
The two languages SQL and PL/SQL serve different purposes but are used together in the management of a database. SQL is the language best suited for carrying out queries upon relations or modification and management of relations. PL/SQL, on the other hand, enhances the power of SQL with the power of procedural programming to meet the needs of more sophisticated business logic and automation in the database.
Understanding the differences between SQL and PL/SQL, their features, and their appropriate use cases is crucial for any database administrator or developer. While SQL is great at organising and accessing data, PL/SQL performs better in situations requiring more control over procedural logic, error handling, and execution flow. Both languages are essential for the smooth administration and operation of contemporary databases, especially in settings where Oracle databases are used.
FAQs
Is PL/SQL only available for Oracle databases?
Yes, PL/SQL is an in-house language of the Oracle Corporation intended for working exclusively in Oracle Databases. It allows executing complex database queries with exception handling in the databases.
Which is easier to learn, SQL or PL/SQL?
Because SQL is declarative, it is easier to learn than PL/SQL, which has a higher learning curve because of its procedural capabilities.
Can we SQL in PL/SQL?
Yes, PL/SQL and SQL are fully integrated, enabling the execution of SQL queries inside PL/SQL blocks. When the users want more control over their query, they prefer using PL/SQL as it provides the best exception handling, running groups of queries, and much more.
What is the main difference between SQL and PL SQL?
The main difference between the two is that SQL is a query language while PL/SQL is a procedural language. SQL provides users with the ability to improve themselves as much as possible by giving them control and limits over the data. PL/SQL allows developers to write programs with control structures, manage exceptions, and create reusable modules like functions, procedures, and triggers.
What is the difference between PL SQL and T-SQL?
PL/SQL offers more procedural capabilities as compared to SQL. Also, T-SQL is less generic than normal SQL as it is centred around a particular database management system. PL/SQL is specific to Oracle databases, but T-SQL attaches itself to Microsoft SQL Server. This however does not mean that they cannot be used for similar reasons. For instance, PL/SQL or T-SQL could be used to implement complex business logic, do automation, database operations, etc.
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