The Difference Between SQL and PL/SQL

Written by Coursera Staff • Updated on

Familiarise yourself with what SQL and PL/SQL are to understand the difference between SQL and PLSQL, and explore their execution methods.

[Featured Image] A programmer with headphones on sits at his desk with his laptop and ponders the difference between SQL and PL/SQL.

Structured query language (SQL) and procedural language extension to structured query language (PL/SQL) are relational database languages used to help organisations handle and store large amounts of data. While they share this similarity, they also have quite a few differences, including how well they run, handle errors, and interface with databases. In the upcoming segments, we will look into the prime disparities between SQL and PL/SQL.

What is SQL?

SQL is a non-procedural programming language used to interact with relational databases. Leveraging SQL makes accessing, controlling, and retrieving data from any database easy. It efficiently manages, creates, accesses, and modifies the relational database. Unlike procedural languages, SQL offers a higher level of abstraction and is highly upgradeable and portable. IBM researchers created this language to assist end users in interacting with different database management systems (DBMS) based on availability.

What is PL/SQL?

PL/SQL is a procedural language based on SQL used to write code blocks. It adds features such as looping and branching to the already powerful SQL. This block-structured language, which Oracle developed to build on SQL's capabilities, enables software developers and programmers to utilise the strength of SQL and procedural statements. With it, you can create web applications and server pages with reduced traffic and more incredible processing speed.

Difference between SQL and PL/SQL

With a basic understanding of these two languages, take a look at the essential differences between SQL and PL/SQL:

Non-procedural languageProcedural language
Used to execute queries in relational databases, such as create table, insert table, and delete tableUsed to write program blocks, functions, procedures, triggers, cursors, and packages
Executes only a single operation at a timeExecutes blocks of code simultaneously
Does not reduce network trafficReduces network traffic
Does not increase processing speedIncreases processing speed
Does not support variablesSupports variable constraints and data types
Uses DDL and DML to write commands and queriesUses functions, variables, triggers, conditional statements, and control structures to write code blocks
Can embed PL/SQL within itselfCannot embed SQL within itself
Interacts directly with the database serverDoes not interact directly with the database server
Does not support control structuresSupports control structures, such as for loop, while loop, and if-else
Does not feature error handlingHandles errors and exceptions

Execution in SQL

SQL contains statements, which are instructions through which you can inform SQL about the task. SQL then performs the task by compiling the instructions and navigating the database.

It is necessary to use certain SQL statements to carry out every operation. A few terms in SQL are also designated for carrying out particular tasks, such as SELECT, UPDATE, and DELETE. 

  • Data definition: These statements define, drop, or alter database objects. They're called data definition language (DDL) statements. Examples include CREATE TABLE, REVOKE, and ANALYSE.

  • Data manipulation: Data manipulation language (DML) statements are used to access, create, or change data in any existing database structure. Examples of DML are UPDATE, SELECT, DELETE, and EXPLAIN.

  • Transaction control: These statements manage changes made by DML statements. Examples include ROLLBACK, COMMIT, SAVEPOINT, and SET TRANSACTION. 

  • Session control: These statements manage the properties of a user's session via ALTER SESSION and SET ROLE commands.

  • System control: The database attributes are managed through system control statements using the ALTER SYSTEM command.

Execution in PL/SQL

Logical blocks make a PL/SQL program, making PL/SQL a block-structured language. Sub-blocks may be present in a PL/SQL application. Each block is divided into a declarative section, an executable section, and an exception section. Like in many other programming languages, they are determining variables is important before use. Error management has a separate section in PL/SQL. Each PL/SQL block starts with the keyword BEGIN or DECLARE and terminates with the END keyword.

Advantages of SQL

Businesses benefit from using business intelligence tools that run on SQL. The language is essential for data science tools, and you can conduct data testing and data manipulation through SQL. Additional advantages of using SQL include the following:

  • It promotes efficient query processing, boosting the amount of data retrieval. 

  • In comparison to procedural languages, SQL may be an advanced language with a higher level of abstraction.

  • It is highly portable, as it can be employed in programs for PCs, tablets, and independent laptops that run on Windows, Mac, Linux, or mobile phones. 

  • Where it is available, it allows system personnel and end users to interact with various database management systems.

Advantages of PL/SQL

Web applications made with PL/SQL include user interfaces and the back-end logic for websites. PL/SQL is considered a portable and high-performance language. The following are some advantages of PL/SQL:

  • Scalability: Its stored subprograms centralise application processing on the database server, thus enhancing scalability.

  • Block structures: These consist of blocks of codes where each block constitutes a logical module or task unit. PL/SQL blocks are frequently saved in the data and used again.

  • Support for object-oriented programming: It allows defining object types used in object-oriented designs. It supports OOP with abstract data types.

  • Procedure language capabilities: PL/SQL includes procedural language structures like if-else statements, loops, and examples of conditional statements.

  • Enhanced performance: PL/SQL engine processes many SQL statements simultaneously as one block, improving performance and lowering network traffic.

  • Error handling: PL/SQL appropriately manages errors or exceptions throughout a program's execution. The course of action taken to resolve exceptions depends on their type.

Next steps

Now that you understand the difference between SQL and PL/SQL, you can broaden your understanding and learn more with a Google Data Analytics Professional Certificate on Coursera.  It’s an opportunity to develop a detailed understanding of data analytics or upgrade your knowledge.

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