[note] on May 27, 2022, MySQL is operated through pychart

1. adopt pycharm insert data

RIGHT Example：

# example01 -  Connect MySQL Database inserts data 

# SQL Injection - SQL Injection attack 
#  Experience ： You must not be able to use string splicing or formatting to assemble dynamic SQL, Or you'll face it SQL Injection attack .

import pymysql
from pymysql.cursors import Cursor

no = input(' Please enter the department number ：')
name = input(' Please enter the Department name ：')
location = input(' Please enter the Department Address ：')

# 1.  Create connection 
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2.  Get cursor object 
    with conn.cursor() as cursor:   # type: Cursor

        # 3.  Execute through cursor objects SQL sentence 
        affected_rows = cursor.execute(
            'select dno from tb_dept where dno = (%s)',
            (no,)
        )
        if affected_rows == 0:
            affected_rows = cursor.execute(
                'insert into tb_dept (dno, dname, dloc) '
                'values (%s, %s, %s)',
                (no, name, location)
            )
            if affected_rows == 1:
                print(' Department added successfully ！！！')
        else:
            print(' Department already exists ')

    # 4.  Manual submission ( Let the previous operation take effect )
    conn.commit()

except pymysql.MySQLError as err:
    # 4.  Manual rollback ( Undo the previous operation )
    conn.rollback()
    print(err)

finally:
    # 5.  Close the connection 
    conn.close()

Common mistakes ：

2. adopt pycharm Delete data

RIGHT Example：

# example02 -  Connect MySQL Database delete data 

import pymysql
from pymysql.cursors import Cursor

no = input(' Please enter the department number ：')

# 1.  Create connection 
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2.  Get cursor object 
    with conn.cursor() as cursor:   # type: Cursor

        # 3.  Execute through cursor objects SQL sentence 
        affected_rows = cursor.execute(
            'select dno from tb_dept where dno = (%s)',
            (no,)
        )
        if affected_rows == 0:
            print(' Already deleted ')

        else:
            affected_rows = cursor.execute(
                'delete from tb_dept where dno = (%s) ',
                (no,)
            )
            if affected_rows == 1:
                print(' Delete Department succeeded ！！！')

    # 4.  Manual submission ( Let the previous operation take effect )
    conn.commit()

except pymysql.MySQLError as err:
    # 4.  Manual rollback ( Undo the previous operation )
    conn.rollback()
    print(err)

finally:
    # 5.  Close the connection 
    conn.close()

3. adopt pycharm Change data

RIGHT Example：

# example03 -  Connect MySQL Database changes data 

import pymysql
from pymysql.cursors import Cursor

no = input(' Please enter the department number ：')
name = input(' Please enter the Department name ：')
location = input(' Please enter the Department Address ')

# 1.  Create connection 
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2.  Get cursor object 
    with conn.cursor() as cursor:   # type: Cursor

        # 3.  Execute through cursor objects SQL sentence 
        affected_rows = cursor.execute(
            'update tb_dept set dname = %s, dloc = %s where dno = %s',
            (name, location, no)
        )
        if affected_rows == 1:
            print(' The update is successful ')

    # 4.  Manual submission ( Let the previous operation take effect )
    conn.commit()

except pymysql.MySQLError as err:
    # 4.  Manual rollback ( Undo the previous operation )
    conn.rollback()
    print(err)

finally:
    # 5.  Close the connection 
    conn.close()

4. adopt pycharm Check data

# example04 -  Connect MySQL Check the data in the database 

import pymysql
import csv
from pymysql.cursors import Cursor, DictCursor

f = open(' The employee table .csv', 'w', encoding='utf-8', newline='')
writer = csv.writer(f)
writer.writerow([' Employee number ', ' Employee name ', ' Employee position ', ' Employee supervisor ', ' Employee's monthly salary ', ' Employee bonus ', ' Department No '])

# 1.  Create connection 
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2.  Get cursor object 
    with conn.cursor() as cursor:   # type: Cursor

        # 3.  Execute through cursor objects SQL sentence 
        affected_rows = cursor.execute(
            'select eno, ename, job, mgr, sal, comm, dno from tb_emp'
        )
        # 4.  Grab data through cursor objects 
        while data := cursor.fetchone():
            writer.writerow(data)

except pymysql.MySQLError as err:
    print(err)

finally:
    # 5.  Close the connection 
    conn.close()