Python3 connects to MySQL
This article introduces the basic use of PyMySQL, a third-party library for Python3 to connect to MySQL.
Introduction to PyMySQL
PyMySQL is a library for connecting to MySQL servers in Python 3.x, and mysqldb in Python 2.
You can also use PyMySQL to connect to MySQL databases in Django.
PyMySQL installation
pip3 install PyMySQL
Connect to the database
Precautions
Note before proceeding with the following content in this article:
- You have a MySQL database, and it has been started.
- You have a username and password that can connect to the database
- You have a database that you have permission to operate on
basic use
# Import the pymysql module import pymysql # connect database conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8") # Get a cursor object that can execute SQL statements cursor = conn.cursor() # Define the SQL statement to execute sql = """ CREATE TABLE USER1 ( id INT auto_increment PRIMARY KEY , name CHAR(10) NOT NULL UNIQUE, age TINYINT NOT NULL )ENGINE=innodb DEFAULT CHARSET=utf8; """ # Execute the SQL statement cursor.execute(sql) # close the cursor object cursor.close() # close the database connection conn.close()
Return data in dictionary format:
# Import the pymysql module import pymysql # connect database conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8") # Get a cursor that can execute an SQL statement and return the result as a dictionary cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) # Define the SQL statement to execute sql = """ CREATE TABLE USER1 ( id INT auto_increment PRIMARY KEY , name CHAR(10) NOT NULL UNIQUE, age TINYINT NOT NULL )ENGINE=innodb DEFAULT CHARSET=utf8; """ # Execute the SQL statement cursor.execute(sql) # close the cursor object cursor.close() # close the database connection conn.close()
Notice:
charset="utf8", do not write the encoding as "utf-8"
Add, delete, modify and check operations
increase
# Import the pymysql module import pymysql # connect database conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8") # Get a cursor object that can execute SQL statements cursor = conn.cursor() sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);" username = "Alex" age = 18 # Execute the SQL statement cursor.execute(sql, [username, age]) # commit transaction conn.commit() cursor.close() conn.close()
Failed to insert data rollback
# Import the pymysql module
import pymysql
# connect database
conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8")
# Get a cursor object that can execute SQL statements
cursor = conn.cursor()
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
username = "Alex"
age = 18
try:
# Execute the SQL statement
cursor.execute(sql, [username, age])
# commit transaction
conn.commit()
except Exception as e:
# If there is an exception, roll back the transaction
conn.rollback()
cursor.close()
conn.close()
Get the ID of the inserted data (used in the association operation)
# Import the pymysql module
import pymysql
# connect database
conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8")
# Get a cursor object that can execute SQL statements
cursor = conn.cursor()
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
username = "Alex"
age = 18
try:
# Execute the SQL statement
cursor.execute(sql, [username, age])
# commit transaction
conn.commit()
# After submitting, get the ID of the data just inserted
last_id = cursor.lastrowid
except Exception as e:
# If there is an exception, roll back the transaction
conn.rollback()
cursor.close()
conn.close()
batch execution
# Import the pymysql module
import pymysql
# connect database
conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8")
# Get a cursor object that can execute SQL statements
cursor = conn.cursor()
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
data = [("Alex", 18), ("Egon", 20), ("Yuan", 21)]
try:
# Batch execute multiple insert SQL statements
cursor.executemany(sql, data)
# commit transaction
conn.commit()
except Exception as e:
# If there is an exception, roll back the transaction
conn.rollback()
cursor.close()
conn.close()
delete
# Import the pymysql module
import pymysql
# connect database
conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8")
# Get a cursor object that can execute SQL statements
cursor = conn.cursor()
sql = "DELETE FROM USER1 WHERE id=%s;"
try:
cursor.execute(sql, [4])
# commit transaction
conn.commit()
except Exception as e:
# If there is an exception, roll back the transaction
conn.rollback()
cursor.close()
conn.close()
change
# Import the pymysql module
import pymysql
# connect database
conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8")
# Get a cursor object that can execute SQL statements
cursor = conn.cursor()
# SQL statement to modify data
sql = "UPDATE USER1 SET age=%s WHERE name=%s;"
username = "Alex"
age = 80
try:
# Execute the SQL statement
cursor.execute(sql, [age, username])
# commit transaction
conn.commit()
except Exception as e:
# If there is an exception, roll back the transaction
conn.rollback()
cursor.close()
conn.close()
check
Query a single piece of data
# Import the pymysql module import pymysql # connect database conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8") # Get a cursor object that can execute SQL statements cursor = conn.cursor() # SQL statement to query data sql = "SELECT id,name,age from USER1 WHERE id=1;" # Execute the SQL statement cursor.execute(sql) # Get a single query data ret = cursor.fetchone () cursor.close() conn.close() # print the query result print (ret)
Query multiple pieces of data
# Import the pymysql module import pymysql # connect database conn = pymysql.connect(host="your database address", user="username", password="password", database="database name", charset="utf8") # Get a cursor object that can execute SQL statements cursor = conn.cursor() # SQL statement to query data sql = "SELECT id,name,age from USER1;" # Execute the SQL statement cursor.execute(sql) # Get multiple query data ret = cursor.fetchall() cursor.close() conn.close() # print the query result print (ret)
Advanced usage
# Get the specified amount of data cursor.fetchmany(3) # The cursor moves by 1 absolute position cursor.scroll(1, mode="absolute") # The cursor moves 1 according to the relative position (current position) cursor.scroll(1, mode="relative")