Python MySQL Tutorial – How to UPDATE Table Data Using Python

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Tags:- MySQL Python

Updating records in a MySQL table is a common task when building applications that manage data. In this tutorial, you'll learn how to use Python to update existing records in a MySQL database using the mysql-connector-python library.


Table of Contents

  1. What is the UPDATE Statement?

  2. Prerequisites

  3. Install MySQL Connector

  4. Connect to MySQL Using Python

  5. Update a Single Record

  6. Update Multiple Records

  7. Use Variables in Update Queries

  8. Full Working Example

  9. Tips and Common Pitfalls


✅ 1. What is the UPDATE Statement?

The UPDATE SQL statement is used to modify existing data in one or more rows of a table.

Syntax:

UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;

⚠️ Always use a WHERE clause to avoid updating all rows in the table.


⚙️ 2. Prerequisites

Before you begin, make sure you have:

  • Python installed

  • MySQL Server running

  • A MySQL database and a table with data

  • The mysql-connector-python library installed


3. Install MySQL Connector

Install the official MySQL connector using pip:

pip install mysql-connector-python

4. Connect to MySQL Using Python

import mysql.connector

db = mysql.connector.connect(
    host="localhost",
    user="your_username",
    password="your_password",
    database="your_database"
)

cursor = db.cursor()

5. Update a Single Record

To update a single record:

sql = "UPDATE users SET age = %s WHERE id = %s"
val = (28, 3)

cursor.execute(sql, val)
db.commit()

print(cursor.rowcount, "record(s) updated")

Explanation:

  • %s is a placeholder for parameters.

  • val is a tuple with the new age and the user ID.

  • db.commit() saves the changes to the database.


6. Update Multiple Records with Conditions

Update multiple rows that match a condition:

sql = "UPDATE users SET city = %s WHERE country = %s"
val = ("Toronto", "Canada")

cursor.execute(sql, val)
db.commit()

print(cursor.rowcount, "record(s) updated")

This updates the city for all users in Canada.


7. Use Variables Dynamically in Queries

You can create dynamic queries with user input:

user_id = 4
new_email = "[email protected]"

sql = "UPDATE users SET email = %s WHERE id = %s"
val = (new_email, user_id)

cursor.execute(sql, val)
db.commit()

print("Email updated successfully.")

8. Full Working Example

import mysql.connector
from mysql.connector import Error

def update_user_email(user_id, new_email):
    try:
        db = mysql.connector.connect(
            host="localhost",
            user="root",
            password="your_password",
            database="mydatabase"
        )

        cursor = db.cursor()

        sql = "UPDATE users SET email = %s WHERE id = %s"
        val = (new_email, user_id)

        cursor.execute(sql, val)
        db.commit()

        print(f"{cursor.rowcount} record(s) updated.")

    except Error as e:
        print("Error updating data:", e)

    finally:
        if db.is_connected():
            db.close()
            print("Database connection closed.")

# Call the function
update_user_email(2, "[email protected]")

⚠️ 9. Tips and Common Pitfalls

Pitfall Solution
Forgetting WHERE clause Will update all rows—use WHERE carefully
Not using .commit() Changes won’t be saved to the database
Wrong column or table name Double-check your SQL syntax
Using raw input in queries Always use parameterized queries to avoid SQL injection

✅ Best Practices

  • Always use WHERE to target specific rows.

  • Use placeholders (%s) to prevent SQL injection.

  • Check cursor.rowcount to see how many records were affected.

  • Test queries in MySQL first before using them in Python.


Summary Table

Task Code
Update one record UPDATE users SET age = %s WHERE id = %s
Commit changes db.commit()
Use placeholders cursor.execute(sql, val)
Check affected rows cursor.rowcount

Final Thoughts

Updating MySQL tables using Python is a fundamental task when working with databases. By using parameterized queries and committing changes properly, you can safely and efficiently update your data. Always back up your data and test your queries before applying them to production.

 

Tips and Tricks


What is pass in Python?

Python | Pass Statement

The pass statement is used as a placeholder for future code. It represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written.

 

def myfunction():
    pass

 


How can you generate random numbers?

Python | Generate random numbers

Python provides a module called random using which we can generate random numbers. e.g: print(random.random())

 

 

We have to import a random module and call the random() method as shown below:

 import random

 print(random.random())

The random() method generates float values lying between 0 and 1 randomly.


To generate customized random numbers between specified ranges, we can use the randrange() method
Syntax: randrange(beginning, end, step)
 

import random

print(random.randrange(5,100,2))

 


What is lambda in Python?

Python | Lambda function

A lambda function is a small anonymous function. This function can have any number of parameters but, can have just one statement.
 

 

Syntex: 
lambda arguments : expression
 

a = lambda x,y : x+y

print(a(5, 6))

It also provides a nice way to write closures. With that power, you can do things like this.

def adder(x):
    return lambda y: x + y

add5 = adder(5)

add5(1)    #6

As you can see from the snippet of Python, the function adder takes in an argument x and returns an anonymous function, or lambda, that takes another argument y. That anonymous function allows you to create functions from functions. This is a simple example, but it should convey the power lambdas and closures have.
 


What is swapcase() function in the Python?

Python | swapcase() Function

It is a string's function that converts all uppercase characters into lowercase and vice versa. It automatically ignores all the non-alphabetic characters.
 

string = "IT IS IN LOWERCASE."  

print(string.swapcase())  

 


How to remove whitespaces from a string in Python?

Python | strip() Function | Remove whitespaces from a string 

To remove the whitespaces and trailing spaces from the string, Python provides a strip([str]) built-in function. This function returns a copy of the string after removing whitespaces if present. Otherwise returns the original string.
 

string = "  Python " 
 
print(string.strip())  

 


What is the usage of enumerate() function in Python?

Python | enumerate() Function

The enumerate() function is used to iterate through the sequence and retrieve the index position and its corresponding value at the same time.
 

lst = ["A","B","C"] 
 
print (list(enumerate(lst)))

#[(0, 'A'), (1, 'B'), (2, 'C')]

 


Can you explain the filter(), map(), and reduce() functions?

Python | filter(), map(), and reduce() Functions

  • filter()  function accepts two arguments, a function and an iterable, where each element of the iterable is filtered through the function to test if the item is accepted or not.
    >>> set(filter(lambda x:x>4, range(7)))
    
    # {5, 6}
    
    

     

  • map() function calls the specified function for each item of an iterable and returns a list of result

    >>> set(map(lambda x:x**3, range(7)))
    
    # {0, 1, 64, 8, 216, 27, 125}

     

  • reduce() function reduces a sequence pair-wise, repeatedly until we arrive at a single value..
     

    >>> reduce(lambda x,y:y-x, [1,2,3,4,5])
    
    # 3
    

    Let’s understand this:

    2-1=1
    3-1=2
    4-2=2
    5-2=3

    Hence, 3.

 


What is a namedtuple?

Python | namedtuple

A namedtuple will let us access a tuple’s elements using a name/label. We use the function namedtuple() for this, and import it from collections.

>>> from collections import namedtuple

#format
>>> result=namedtuple('result','Physics Chemistry Maths') 

#declaring the tuple
>>> Chris=result(Physics=86,Chemistry=92,Maths=80) 

>>> Chris.Chemistry
# 92

 


Write a code to add the values of same keys in two different dictionaries and return a new dictionary.

We can use the Counter method from the collections module

from collections import Counter

dict1 = {'a': 5, 'b': 3, 'c': 2}
dict2 = {'a': 2, 'b': 4, 'c': 3}

new_dict = Counter(dict1) + Counter(dict2)


print(new_dict)
# Print: Counter({'a': 7, 'b': 7, 'c': 5})


 


Python In-place swapping of two numbers

 Python | In-place swapping of two numbers

>>> a, b = 10, 20
>>> print(a, b)
10 20

>>> a, b = b, a
>>> print(a, b)
20 10

 


Reversing a String in Python

Python | Reversing a String

>>> x = 'PythonWorld'
>>> print(x[: : -1])
dlroWnohtyP

 


Python join all items of a list to convert into a single string

Python | Join all items of a list to convert into a single string

>>> x = ["Python", "Online", "Training"]
>>> print(" ".join(x))
Python Online Training

 


python return multiple values from functions

Python | Return multiple values from functions

>>> def A():
	return 2, 3, 4

>>> a, b, c = A()

>>> print(a, b, c)
2 3 4

 


Python Print String N times

Python | Print String N times

>>> s = 'Python'
>>> n = 5

>>> print(s * n)
PythonPythonPythonPythonPython

 


Python check the memory usage of an object

Python | Check the memory usage of  an object

>>> import sys
>>> x = 100

>>> print(sys.getsizeof(x))
28