This pdf is about my sql

2. Now we will access and manipulate our database using a python program.
To connect our python script to a MySQL database, we need some special functions,
for which we have a library mysql connector.
Import mysql.connector as sqlcon
we can send our queries from script to the database
Interface Python with MySQL
Step 1 :

3. To establish the connection to MySQL Database we’ll use connect( ) function.
<connection-object> = sqlcon.connect(host=<host-name>, user=<username>,
passwd=<password> [, database=<database>])
mycon=sqlcon.connect(host='localhost', user='rahul',passwd='ILoveNeha123',database = 'test')
if mycon.is_connected():
print('Successfully Connected to MySQL database')
Connecting DB to object
Step 2 :

4. When we send our query to the server where it gets executed, the result(what we
asked in query) is sent back to us in one go. But if we want to access the retrieved
data one row at a time, we can’t do it directly. A control structure called database
cursor can be created that gets access of all the records retrieved as per query and
allows us to traverse the result row by row.
cur = mycon.cursor( )
cursor object connector object cursor function
Creating cursor instance
Step 3 :

5. After making the cursor, we can execute SQL queries using execute( ) function as
per following syntax :
<cursor-object>.execute(<sql query string>)
e.g. cur.execute('select * from student')
*This will store the retrieved records in the cursor object.
Executing SQL query
Step 4 :

6. Now that records have been retrieved from the database using our Query, we
need to extract the records from cursor or we can say, we need to fetch the data
using fetch() functions.
1. <data>=<cursor>.fetchall() returns all the records retrieved in a tuple form.
2. <data>=<cursor>.fetchone() returns one record as a tuple or list, next time
next record and so on. Returns None if no records.
3. <data>=<cursor>.fetchmany(n) returns ‘n’ records as a tuple, empty tuple if no
records.
4. <var>=<cursor>.rowcount( ) returns number of rows retrieved from the
cursor so far.
Extracting data from cursor
Step 5 :

7. <connector object>.close( )
e.g. mycon.close( )
Cleaning up the Environment
Step 6 :
At last, we close the connection established.

8. Parameterized Queries
n=33
cur.execute( 'SELECT * FROM student WHERE marks>n' )
cur.execute( 'SELECT * FROM student WHERE marks>%s'%(33,) )
cur.execute( '---- WHERE marks>%s AND sec='%s' '%(33,'A') )

9. Parameterized Queries
pass_marks = 33
section = 'A'
query = ' SELECT * FROM student WHERE marks>%s AND sec='%s' '
values = (pass_marks, section)
values2 = (27,'B')
cur.execute(query, values)
cur.execute(query, values2)

10. 'I will score { } out of { }'.format(27,70)
'I will score {0} out of {1}'.format(33,100)
'I will score {marks} out of {total}'.format(total=100, marks=33)
s='SELECT * FROM stu WHERE mrk>{} AND sec='{}''.format(60, ‘A’)
Parameterized Queries

11. Inserting Queries
By similarly using the execute( ) function, we can insert data in tables.
cur.execute('INSERT INTO student(rollno, name, marks)
VALUES ({}, '{}', {})'.format(141,'Harsh', 99))
mycon.commit( )
cur.execute('UPDATE student SET marks ={}
WHERE marks={}'.format(94,96))
mycon.commit( )