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PostgreSQL, a powerful open-source relational database management system, offers robust features for creating stored procedures, functions, and views.
Stored procedures are reusable blocks of SQL code stored in the database server, executed with a single call. They enhance code modularity and security by centralizing logic within the database.
Functions in PostgreSQL provide a mechanism to encapsulate frequently used logic, returning a value upon execution. They can simplify complex calculations and data manipulations.
Views offer a virtual representation of data based on a predefined SQL query. They provide a convenient way to simplify complex queries and hide underlying complexity from users.
Together, these features empower developers to optimize performance, enhance security and streamline database interactions in PostgreSQL.
Key Takeaways
Achieve a solid understanding of stored procedures, functions, and views, including how to create them.
Understand the distinctions among them.
Stored Procedures
Stored procedures in PostgreSQL are sets of SQL and procedural language statements grouped together as a single unit. They are stored in the database and can be executed by calling their name, passing parameters if necessary.
Stored procedures are capable of executing complex operations, transactions, and business logic within the database. They can incorporate control flow statements such as loops, conditionals, and exception handling to enhance functionality and robustness.
Stored procedures are commonly utilized for data manipulation, transaction control, and executing complex database operations.
Syntax:
CREATE OR REPLACE PROCEDURE <<procedure_name>> (IN {{input_parameters}} )
AS $$
BEGIN
<< SQL statement goes here >>
END;
$$ language plpgsql;
Once Created, you can call this stored procedure by using the following syntax:
CALL <<procedure_name(input_value)>>
Stored procedures can perform various data manipulation operations, including INSERT, UPDATE, DELETE, and SELECT queries. They can encapsulate complex queries involving multiple tables and relationships.
PostgreSQL supports various procedural languages like PL/pgSQL, PL/Python, PL/Perl, etc. For writing stored procedures, with PL/pgSQL being the most commonly used. This allows us to perform loops, condition checks and handle exceptions.
Since procedures are stored in the database, they can be reused across multiple applications and database sessions.
By executing complex operations on the database server, stored procedures can reduce network traffic and improve performance, especially for operations involving large datasets or complex calculations.
Stored procedures can be part of database transactions, ensuring that a series of operations either succeed or fail as a single atomic unit, maintaining data consistency.
Stored procedures enhance security by limiting direct access to underlying tables and providing controlled access to data through parameterized interfaces.
PostgreSQL allows stored procedures to execute dynamic SQL statements using the EXECUTE command, enabling dynamic query generation based on runtime conditions.
Functions
In PostgreSQL, functions are a powerful feature that helps to encapsulate logic and calculations into reusable units. Functions take input parameters and return values. Input parameters can be of various data types, and the return type can also vary depending on the function's purpose.
Types of Functions:
PostgreSQL supports various types of functions.
Scalar Functions - Returns a single value.
Table Functions - Returns a set of rows.
Aggregate Functions - Operates on a set of values.
Syntax:
CREATE OR REPLACE FUNCTION << function_name>> (in_parameter data_type..)
RETURNS << return_type >> AS $$
BEGIN
<< SQL code goes here >>
END;
$$ LANGUAGE plpgsql;
To call the function:
SELECT <<function_name>> (input_p_values)
Like stored procedures, functions can be written in different procedural languages such as PL/pgSQL, PL/Python, PL/Perl, etc. PL/pgSQL is the most common language used.
Functions can perform various data manipulation operations, including SELECT queries, INSERT, UPDATE, and DELETE operations.
They can encapsulate complex SQL queries involving joins, aggregations, and subqueries.
Functions promote modularity and code reuse. Functions can encapsulate complex SQL queries, calculations, and business logic. They can help optimize performance by executing operations on the server-side, reducing network overhead and improving efficiency.
Functions can generate and execute dynamic SQL statements using the EXECUTE command, allowing for dynamic query generation based on runtime conditions.
They are versatile tools for performing calculations, data transformations, and custom business logic within the database.
Views
In PostgreSQL, views provide a way to present data from one or more tables or other views as if they were a single table. Views are a powerful tool in PostgreSQL for simplifying data access, enhancing security, and improving query performance.
Syntax:
CREATE VIEW <<view_name>> AS
SELECT col_name1, col_name2,...
FROM <<table_name>>
Once we create a view we can query the view like any other table.
SELECT * FROM <<view_name>>
Views are virtual tables that do not store data themselves; instead, they are defined by a query.
Views provide a layer of abstraction over the underlying data, allowing users to interact with complex data structures through simplified interfaces.
Views can be used to restrict access to sensitive data. By granting users access to views instead of underlying tables, you can control which columns or rows they can see, ensuring data security and privacy.
Views encapsulate frequently used queries, promoting code reuse and reducing redundancy.
PostgreSQL's query planner can optimize queries involving views, potentially speeding up query execution.
PostgreSQL's query planner can optimize queries involving views, potentially speeding up query execution.
Difference between SP, Functions and Views
Stored Procedures | Functions | Views |
Accepts parameters | Accepts parameters | Does NOT accept parameters |
Returns multiple values/table | Returns a value | Returns a single table |
Can call a Function and views from a Stored Procedure | Cannot call a SP within the function. But can call Views | Cannot call Stored Procedures, but can call Functions |
Can contain several SQL statements | Can contain several SQL statements | Contain single SELECT statement |
Compiled once and can be called multiple times | Compiled every time it is called. | Not compiled |
A SELECT statement cannot have a procedure call | A SELECT statement can have a function call. | Can be used in a SELECT query |
A Procedure support try-catch block | Function does not support try-catch block | Exceptions cannot be handled |
Not mandatory to return a value | MUST return a value | MUST return a table |
Stored procedures, functions, and views are fundamental database objects in PostgreSQL, each serving distinct purposes and offering unique capabilities.
In summary, stored procedures are for executing complex operations and business logic within the database, functions are for returning values and performing calculations, and views are for providing abstracted and simplified representations of data. Each of these database objects plays a crucial role in database development and management in PostgreSQL.
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