python db connection samples and program

Connecting Python with SQL
Database

OBJECTIVE
To make student
aware about
Connectivity between
frontend -backend

PREREQUISITE
➢Detailed knowledge of Python.
➢MySQL

Point to be Focussed
(3 Important Steps)
➢ Download Python 3.5.3 and then install it
➢ Download MySQL API, exe file will be
downloaded install it.
➢ Install MySQL-Python Connector
➢ Now connect MySQL Server using
Python.

What is MySQLdb
What is Connection
What is a Cursor

• MySQLdb is an interface
for connecting to a MySQL
database server from
Python.
• It implements the
Python Database API and
is built on top of the
MySQL C API.
• Just type the following in
your Python script and
execute it −
#!/usr/bin/python
import MySQLdb
What is MySQLdb

• The next step to using
MySQL in your Python
scripts is to make a
connection to the
database that you wish
to use. All Python DB-
API modules implement
a function
'module_name.connect‘
• This is the function that
is used to connect to the
database, in our case
MySQL..
What is Connection

Connection MySQLdb
Db=MySQLdb.connect
(“localhost”, testuser”,
”test123”, ”TESTDB”)

Connecting to a MySQL database
:
db = MySQLdb.connect(host=MY_HOST, user=MY_USER,
passwd=MY_PASS, db=MY_DB)
Your user name
Your
Password
Name of the
Database
db = MySQLdb.connect("localhost","testuser","test123","TESTDB" )

•The next step is to create a
Cursor object.
•It will let you execute all
the queries you need
•In order to put our new
connnection to good use we
need to create a cursor
object.
•The cursor object is an
abstraction specified in the
Python DB-API
•It gives us the ability to
have multiple seperate
working environments
through the same
connection to the database.
•We can create a cursor by
executing the 'cursor'
function of your database
What is Cursor

Example of Simple Code to Connect MySQL with Python
<? xml version=“1.0” ?>
<land>
<forest>
<Tree>
---------------------------
---------------------------
---------------------------
</Tree>
</forest>
</land>

Creating database Table
➢Once a Database Connection is established, we are ready to create tables using execute( )
method of the created cursor
➢Example
#!/usr/bin/python
import MySQLdb
# Open database connection
# prepare a cursor object using cursor() method
cursor = db.cursor()
# Drop table if it already exist using execute() method.
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
# Create table as per requirement
sql = “ “ "CREATE TABLE EMPLOYEE (FIRST_NAME CHAR(20) NOT NULL,
LAST_NAME CHAR(20),
AGE INT,
SEX CHAR(1),
INCOME FLOAT )“ “ "
cursor.execute(sql)
# disconnect from server
db.close()

Insert Records into databse table
➢Its required to insert records in table for fetching records.
➢Example
#!/usr/bin/python
import MySQLdb
# Open database connection
# prepare a cursor object using cursor() method
# Prepare SQL query to INSERT a record into the database.
sql = """INSERT INTO EMPLOYEE(FIRST_NAME,LAST_NAME, AGE, SEX, INCOME)
VALUES('Mac', 'Mohan', 20, 'M', 2000)"""
try:
# Execute the SQL command
cursor.execute(sql)
# Commit your changes in the database
db.commit()
except:
# Rollback in case there is any error
db.rollback()
db.close()

Read Records (Select) into databse
table
➢Read operation on any database means to fetch some useful
information from the database.
➢We can use fetchone() method to fetch single record
➢fetchall() method to fetch multiple values from a database table.
➢fetchone() − It fetches the next row of a query result set.
A result set is an object that is returned when a
cursor object is used to query a table.
fetchall() − It fetches all the rows in a result set.
If some rows have already been extracted from the
result set, then it retrieves the remaining rows from the
result set.
rowcount − This is a read-only attribute and returns the number of
rows that were affected by an execute() method.

➢Example
import MySQLdb
sql = "SELECT * FROM EMPLOYEE WHERE INCOME > '%d'" % (1000)
try:
cursor.execute(sql)
# Fetch all the rows in a list of lists.
results = cursor.fetchall()
for row in results:
fname = row[0] lname = row[1]
age = row[2] sex = row[3]
income = row[4]
# Now print fetched result
print "fname=%s,lname=%s,age=%d,sex=%s,income=%d" %
(fname, lname, age, sex, income )
except:
print "Error: unable to fecth data"
db.close()

Update information into databse
table
➢UPDATE Operation on any database means to update one or more records, which
are already available in the database.
➢The following procedure updates all the records having SEX as 'M'. Here, we
increase AGE of all the males by one year.
➢Example
import MySQLdb
sql = "UPDATE EMPLOYEE SET AGE = AGE + 1 WHERE SEX = '%c'" % ('M')
try:
cursor.execute(sql)
db.commit()
except:
db.rollback()

Delete information into databse
table
➢DELETE operation is required when you want to delete some records from your
database. Following is the procedure to delete all the records from EMPLOYEE
where AGE is more than 20
➢Example
import MySQLdb
sql = "DELETE FROM EMPLOYEE WHERE AGE > '%d'" % (20)
try:
cursor.execute(sql)
db.commit()
except:
db.rollback()

➢To disconnect Database connection,
use close() method.
db.close()
Disconnecting Database

python db connection samples and program

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