31
Dec

Importance of Stored Procedure in SQL

A stored procedure in SQL is a precompiled set of one or more SQL statements that can be executed as a single unit. It encapsulates a series of actions or operations to be performed, enhancing code reusability and maintainability.

Stored procedures accept input parameters, perform computations, and return results, contributing to efficient database management. They are stored on the database server, reducing network traffic and improving performance. Additionally, stored procedures enhance security by allowing controlled access to the underlying data.

These procedures are commonly used to implement business logic, enforce data integrity, and streamline complex database operations. They simplify application development by providing a centralized and standardized approach to common tasks.

With the ability to be called from various applications, stored procedures facilitate seamless integration between front-end applications and databases. Overall, stored procedures play a pivotal role in promoting modularity, reducing redundancy, and ensuring the integrity of database transactions.

Create a stored procedure:

1. Connect to Your Database:

Ensure that you are connected to the PostgreSQL database where you want to create the stored procedure. You can use a tool like pgAdmin or connect via the command line.

Reference: SQLAlchemy

2. Define the Stored Procedure:

Let’s create a basic stored procedure that retrieves employee information based on a provided department ID. In this example, we’ve created a function named get_employee_by_department that takes a department_id as an input parameter. The function returns a table with columns employee_name and employee_salary.

CREATE OR REPLACE FUNCTION: This statement is used to create a new function or replace an existing one.

RETURNS TABLE: Specifies the structure of the result set that the function will return.

$$: Delimiters for the function body.

BEGIN and END: Define the beginning and end of the function body.

RETURN QUERY: This statement is used to return the result set based on the provided SQL query.Execute the Stored Procedure: After creating the stored procedure, you can execute it by calling the function with the desired parameters.

Execute the Stored Procedure: After creating the stored procedure, you can execute it by calling the function with the desired parameters.

The SQL statement SELECT * FROM get_employee_by_department(1); is a correct and valid way to execute the stored procedure in PostgreSQL. The CALL statement is an alternative syntax, and both approaches are acceptable.

Difference between stored procedure and function:

 Stored procedureFunction
ExecutionStored procedures are precompiled sets of one or more SQL statements. They are stored in the database and can be executed explicitly by calling their name.Functions are also precompiled sets of one or more SQL statements. However, they are typically designed to return a single value or a result set. Functions can be used in SQL queries just like any other expression.
Return TypeStored procedures may or may not return values. They can have input parameters and can also produce output, but they don’t necessarily return a result set.Functions must return a value. They are explicitly designed to be used in SQL statements where a result is expected.
Transaction ManagementStored procedures can be used to group a set of SQL statements into a transaction. This allows for more complex operations where multiple SQL statements need to be executed as a single unit.Functions are generally not used to manage transactions. They are more focused on providing a specific result based on the input parameters.
Access to system functionsStored procedures often have access to system functions and procedures provided by the database system, allowing for more extensive control and manipulation of data.Functions may or may not have access to system functions, depending on the specific database system and the type of function (e.g., scalar function, table-valued function).
Security and permissionsStored procedures can be assigned specific permissions, and users can be granted or denied the ability to execute them.Functions can also be assigned specific permissions, but their usage and purpose are often more straightforward compared to stored procedures.

Function

A simple example of a function in PostgreSQL that concatenates the first and last names of an employee.

In this example: The function is named get_full_name. It takes a single input parameter, employee_id, representing the ID of the employee for whom we want to retrieve the full name. The function returns a VARCHAR value, which is the concatenated full name.

Reference: Functions in PSQL

In PostgreSQL, the terms “function” and “stored procedure” are often used interchangeably because both are created using the CREATE OR REPLACE FUNCTION syntax. The primary difference between them is more about convention and usage patterns than a strict technical distinction in PostgreSQL.

Reference: postgresql

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