Oracle PL SQL Tutorials
Welcome to Oracle PL SQL Tutorials. The objective of these tutorials is to provide in depth understand of Oracle PL SQL .
In addition to free Oracle Oracle PL SQL Tutorials, we will cover common interview questions, issues and how to’s of Oracle PL SQL .
Introduction of Oracle PL SQL Tutorials
PL/SQL stands for Procedural Language extensions to the Structured Query Language (SQL). SQL is a powerful language for both querying and updating data in relational databases.
Oracle created PL/SQL that extends some limitations of SQL to provide a more comprehensive solution for building mission-critical applications running on Oracle database.
PL/SQL is a combination of SQL along with the procedural features of programming languages. It was developed by Oracle Corporation in the early 90's to enhance the capabilities of SQL.
PL/SQL is one of three key programming languages embedded in the Oracle Database, along with SQL itself and Java.
This Topic will give you great understanding on PL/SQL to proceed with Oracle database and other advanced RDBMS concepts.
The PL/SQL programming language was developed by Oracle Corporation in the late 1980s as procedural extension language for SQL and the Oracle relational database. Following are notable facts about PL/SQL:
-PL/SQL is a completely portable, high-performance transaction-processing language.
-PL/SQL provides a built-in interpreted and OS independent programming environment.
-PL/SQL can also directly be called from the command-line SQL*Plus interface.
-Direct call can also be made from external programming language calls to database.
-PL/SQL's general syntax is based on that of ADA and Pascal programming language.
-Apart from Oracle, PL/SQL is available in TimesTen in-memory database and IBM DB2.
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Features of PL/SQL
PL/SQL has the following features:
-PL/SQL is tightly integrated with SQL.
-It offers extensive error checking.
-It offers numerous data types.
-It offers a variety of programming structures.
-It supports structured programming through functions and procedures.
-It supports object-oriented programming.
-It supports developing web applications and server pages.
PL/SQL Block consists of three sections:
-The Declaration section (optional).
-The Execution section (mandatory).
-The Exception Handling (or Error) section (optional).
The Declaration section of a PL/SQL Block starts with the reserved keyword DECLARE. This section is optional and is used to declare any placeholders like variables, constants, records and cursors, which are used to manipulate data in the execution section. Placeholders may be any of Variables, Constants and Records, which stores data temporarily. Cursors are also declared in this section.
The Execution section of a PL/SQL Block starts with the reserved keyword BEGIN and ends with END. This is a mandatory section and is the section where the program logic is written to perform any task. The programmatic constructs like loops, conditional statement and SQL statements form the part of execution section.
The Exception section of a PL/SQL Block starts with the reserved keyword EXCEPTION. This section is optional. Any errors in the program can be handled in this section, so that the PL/SQL Blocks terminates gracefully. If the PL/SQL Block contains exceptions that cannot be handled, the Block terminates abruptly with errors.
Every statement in the above three sections must end with a semicolon ; . PL/SQL blocks can be nested within other PL/SQL blocks. Comments can be used to document code.
SQL Command Categories
SQL commands are grouped into four major categories depending on their functionality. They are as follows:
Data Definition Language (DDL)
These SQL commands are used for creating, modifying, and dropping the structure of database objects. The commands are CREATE, ALTER, DROP, RENAME, and TRUNCATE.
Data Manipulation Language (DML)
These SQL commands are used for storing, retrieving, modifying, and deleting data. These commands are SELECT, INSERT, UPDATE, and DELETE.
Transaction Control Language (TCL)
These SQL commands are used for managing changes affecting the data. These commands are COMMIT, ROLLBACK, and SAVEPOINT.
Data Control Language (DCL)
These SQL commands are used for providing security to database objects. These commands are GRANT and REVOKE.
Advantages of PL/SQL
PL/SQL has the following advantages:
-SQL is the standard database language and PL/SQL is strongly integrated with SQL. PL/SQL supports both static and dynamic SQL. Static SQL supports DML operations and transaction control from PL/SQL block. Dynamic SQL is SQL allows embedding DDL statements in PL/SQL blocks.
-PL/SQL allows sending an entire block of statements to the database at one time. This reduces network traffic and provides high performance for the applications.
-PL/SQL gives high productivity to programmers as it can query, transform, and update data in a database.
-PL/SQL saves time on design and debugging by strong features, such as exception handling, encapsulation, data hiding, and object-oriented data types.
Applications written in PL/SQL are fully portable.
-PL/SQL provides high security level.
-PL/SQL provides access to predefined SQL packages.
-PL/SQL provides support for Object-Oriented Programming.
-PL/SQL provides support for Developing Web Applications and Server Pages.