SQL using Python and SQLite | Set 2
Last Updated :
06 Feb, 2018
Databases offer numerous functionalities by which one can manage large amounts of information easily over the web, and high-volume data input and output over a typical file such as a text file. SQL is a query language and is very popular in databases. Many websites use MySQL. SQLite is a “light” version that works over syntax very much similar to SQL.
SQLite is a self-contained, high-reliability, embedded, full-featured, public-domain, SQL database engine. It is the most used database engine in the world wide web.
Python has a library to access SQLite databases, called sqlite3, intended for working with this database which has been included with Python package since version 2.5.
In this article we will discuss, how to query database using commands like Update and Delete and also to visualize data via graphs.
It is recommended to go through SQL using Python | Set 1
Updation and Deletion Operation
import sqlite3
conn = sqlite3.connect('mydatabase.db')
conn.execute("UPDATE Student SET name = 'Sam' where unix='B113059'")
conn.commit()
print "Total number of rows updated :", conn.total_changes
cursor = conn.execute("SELECT * FROM Student")
for row in cursor:
print row,
conn.close()
|
Output:
Total number of rows updated : 1
(u'B113053', u'Geek', u'2017-01-11 13:53:39', 21.0),
(u'B113058', u'Saan', u'2017-01-11 13:53:39', 21.0),
(u'B113059', u'Sam', u'2017-01-11 13:53:39', 22.0)
import sqlite3
conn = sqlite3.connect('mydatabase.db')
conn.execute("DELETE from Student where unix='B113058'")
conn.commit()
print "Total number of rows deleted :", conn.total_changes
cursor = conn.execute("SELECT * FROM Student")
for row in cursor:
print row,
conn.close()
|
Output:
Total number of rows deleted : 1
(u'B113053', u'Geek', u'2017-01-11 13:53:39', 21.0),
(u'B113059', u'Sam', u'2017-01-11 13:53:39', 22.0)
Data input by User
import sqlite3
con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table person (name, age, id)")
print ("Enter 5 students names:")
who = [raw_input() for i in range(5)]
print ("Enter their ages respectively:")
age = [int(raw_input()) for i in range(5)]
print ("Enter their ids respectively:")
p_id = [int(raw_input()) for i in range(5)]
n = len(who)
for i in range(n):
cur.execute("insert into person values (?, ?, ?)", (who[i], age[i], p_id[i]))
cur.execute("select * from person")
print cur.fetchall()
|
Output:
(u'Navin', 34, 113053)
(u'Basu', 42, 113058)
(u'Firoz', 65, 113059)
(u'Tim', 47, 113060)
(u'Varun', 54, 113061)
Graphing with SQLite
import matplotlib.pyplot as plt
def graph_data(p_id,age):
plt.plot(p_id, age, color='yellow', linestyle='dashed', linewidth = 3,
marker='*', markerfacecolor='blue', markersize=12)
plt.xlabel('Persons Id')
plt.ylabel('Ages')
plt.show()
print ("Enter 5 students names:")
who = [raw_input() for i in range(5)]
print ("Enter their ages respectively:")
age = [int(raw_input()) for i in range(5)]
print ("Enter their ids respectively:")
p_id = [int(raw_input()) for i in range(5)]
graph_data(p_id,age)
|
In this way we can perform such operations using SQL query to communicate with Database and plot a Graph significantly to draw out its characteristic.
SQL using Python | Set 1
SQL using Python | Set 3 (Handling large data)
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