python mysql data change and query

#!/usr/bin/python

import MySQLdb
def doInsert(cursor,db):
#insert
# Prepare SQL query to INSERT a record into the database.
sql = "UPDATE EMPLOYEE SET AGE = AGE+1 WHERE SEX = '%c'" %('M')
try:
cursor.execute(sql)
db.commit()
except:
db.rollback()

def do_query(cursor,db):
sql = "SELECT * FROM EMPLOYEE \
WHERE INCOME > '%d'" % (1000)
try:
# Execute the SQL command
cursor.execute(sql)
# Fetch all the rows in a list of lists.
results = cursor.fetchall()
print 'resuts',cursor.rowcount
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"

def do_delete(cursor,db):
sql = 'DELETE FROM EMPLOYEE WHERE AGE > {}'.format(20)
try:
cursor.execute(sql)
db.commit()
except:
db.rollback()

def do_insert(cursor,db,firstname,lastname,age,sex,income):
sql = "INSERT INTO EMPLOYEE(FIRST_NAME, \
LAST_NAME, AGE, SEX, INCOME) \
VALUES ('%s', '%s', '%d', '%c', '%d' )" % \
(firstname,lastname,age,sex,income)
try:
cursor.execute(sql)
db.commit()
except:
db.rollback()

# Open database connection
# change this to your mysql account
#connect(server,username,password,db_name)
db = MySQLdb.connect("localhost","root","root","pydb" )
# prepare a cursor object using cursor() method
cursor = db.cursor()
do_query(cursor,db)
doInsert(cursor,db)
do_query(cursor,db)
do_delete(cursor,db)
do_query(cursor,db)
do_insert(cursor,db,'hunter','xue',22,'M',2000)
do_insert(cursor,db,'mary','yang',22,'f',5555)
do_insert(cursor,db,'zhang','xue',32,'M',5000)
do_insert(cursor,db,'hunter','xue',22,'M',333)
do_query(cursor,db)
# disconnect from server
db.close()