How to write custom stored procedures and functions in MySQL using Python

How to use Python to write custom stored procedures and functions in MySQL

MySQL is a commonly used relational database management system, and Python is a powerful programming language. Combining the two allows for more flexible and efficient database operations. Stored procedures and functions in MySQL can help us encapsulate commonly used operation logic and reduce the writing of repeated code. This article will introduce how to use Python to write custom stored procedures and functions, with specific code examples.

1. Preparation
   First, make sure you have installed Python and MySQL database and can connect to the database.
2. Creating databases and tables
   We will use a sample database to demonstrate the use of custom stored procedures and functions. First, create a database named "testdb" and create a table named "users" in it with the following structure:

CREATE DATABASE testdb;

USE testdb;

CREATE TABLE users (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(255),
  age INT,
  email VARCHAR(255)
);

3. Write Python code
   Next, We will write Python code to create custom stored procedures and functions. First, import the necessary modules and connect to the database:

import mysql.connector

mydb = mysql.connector.connect(
  host="localhost",
  user="yourusername",
  password="yourpassword",
  database="testdb"
)

mycursor = mydb.cursor()

4. Writing a custom stored procedure
   Here is an example of creating a custom stored procedure. This stored procedure will query users based on a specified age range and return the results. The syntax of the stored procedure is as follows:

def create_procedure():
  sql = """
CREATE PROCEDURE get_users_by_age(
  IN min_age INT,
  IN max_age INT
)
BEGIN
  SELECT * FROM users WHERE age >= min_age AND age <= max_age;
END
  """
  mycursor.execute(sql)
  mydb.commit()

5. Call a custom stored procedure
   After creating the stored procedure, we can use the following code to call it:

def call_procedure():
  mycursor.callproc("get_users_by_age", (18, 30))
  for result in mycursor.stored_results():
    for row in result.fetchall():
      print(row)

6. Writing custom functions
   In addition to stored procedures, we can also create custom functions. Below is an example of creating a custom function. This function will return the number of users within the specified age range. The syntax of the function is as follows:

def create_function():
  sql = """
CREATE FUNCTION count_users_by_age(
  min_age INT,
  max_age INT
)
RETURNS INT
BEGIN
  DECLARE user_count INT;
  SELECT COUNT(*) INTO user_count FROM users WHERE age >= min_age AND age <= max_age;
  RETURN user_count;
END
  """
  mycursor.execute(sql)
  mydb.commit()

7. Call a custom function
   After creating the function, we can use the following code to call it:

def call_function():
  mycursor.callfunc("count_users_by_age", int, (18, 30))

So far, we have learned how to write custom stored procedures and functions in MySQL using Python. By combining Python with MySQL, we can perform database operations more flexibly and improve code reusability and maintainability.

The complete code is as follows:

import mysql.connector

mydb = mysql.connector.connect(
  host="localhost",
  user="yourusername",
  password="yourpassword",
  database="testdb"
)

mycursor = mydb.cursor()

def create_procedure():
  sql = """
CREATE PROCEDURE get_users_by_age(
  IN min_age INT,
  IN max_age INT
)
BEGIN
  SELECT * FROM users WHERE age >= min_age AND age <= max_age;
END
  """
  mycursor.execute(sql)
  mydb.commit()

def call_procedure():
  mycursor.callproc("get_users_by_age", (18, 30))
  for result in mycursor.stored_results():
    for row in result.fetchall():
      print(row)

def create_function():
  sql = """
CREATE FUNCTION count_users_by_age(
  min_age INT,
  max_age INT
)
RETURNS INT
BEGIN
  DECLARE user_count INT;
  SELECT COUNT(*) INTO user_count FROM users WHERE age >= min_age AND age <= max_age;
  RETURN user_count;
END
  """
  mycursor.execute(sql)
  mydb.commit()

def call_function():
  mycursor.callfunc("count_users_by_age", int, (18, 30))

create_procedure()
call_procedure()
create_function()
call_function()

The above is how to use Python to write custom stored procedures and functions in MySQL. I hope it will be helpful to you. By rationally utilizing stored procedures and functions, we can improve the efficiency and flexibility of database operations and achieve more powerful functions.

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