Psycopg2 postgres python DDL Operaytions (select , Insert , update, create table)

PostgreSQL Python
1. psycopg2-binary : PostgreSQL Adaptor
2.DDL Operations
3.DML Operations

Installation
 pip install psycopg2-binary
 pip3 install psycopg2-binary

Python Connectors
Python
Application
pymongo
sqlite3
mySQL
pyscopg2
Python Module/Connector
Python DB API’s
Request
Response

Steps
1) Create Connection string
2) Open connection
3) Open cursor
4) Execute cursor
5) Close Cursor
6) Close Connection

Connection
Connection class
 Handles connection to database instances
 Encapsulates a database session
Connection String Example
psycopg2.connect(database="sample",user="postgres",password="sample",
host="127.0.0.1", port="5432")
connection.cursor( )
creates a cursor which will be used throughout of your database programming
with Python

Connection Method ( )
connection.commit ( )
 Commits the current transaction
 Changes will not reflect to other connections if not commited
 Default, psycopg opens a transaction before executing the first command
connection.rollback( )
 This method rolls back any changes to the database since the last call to
commit( )
connection.close( )
 This Method closes the database connection.
 If you close your database connection without calling commit() first, your
changes will
be lost!

CURSOR
 Cursor is Class
 Allows Python code to execute PostgreSQL
command in a database session
 Created by
 connection.cursor( ) Method
 cursor.execute( ), cursor.fetch( ),cursor.close( )

Execute( )
cursor.execute (query [, optional parameters])
 Execute a database operation (query or command)
returns None.
 Cursor.execute(“select * from test”)
 The returned values can be retrieved using fetch*( )
methods
cursor.executemany(query, vars_list)
 Execute a database operation (query or command)
against all parameter tuples or mappings found in
the sequence vars_list

Call Procedures
 cursor.callproc(procname[, parameters])
- Call database stored procedure
- The sequence of parameters must contain one entry for
each argument that the procedure expects
- Overloaded procedure supported
- The procedure may provide a result set as output.
- This is then made available through the standard fetch*()
methods

Fetch()
 cursor.fetchone( )
- Fetch the next row of a query result set, returning a single tuple
 cursor.fetchall( )
- This routine fetches all (remaining) rows of a query result, returning a
list. An empty list is returned when no rows are available.
 cursor.fetchmany([size=cursor.arraysize])
- Fetch the next set of rows of a query result, returning a list of
tuples.An empty list is returned when no more rows are available.

Cursor.*
Cursor.rowcount
This read-only attribute which returns the total number of database rows that
have been modified, inserted, or deleted by the last last execute*().
Cursor.query
Returns last executed query

DDL/DML OPERATIONS
-- Create Table
-- Drop Table
-- Insert Record
-- Update Record
-- Select Record
-- Delete Record

List Database
#Import library
import psycopg2
#Open Connection
conn = psycopg2.connect(database="postgres",
user='postgres', password='postgres',
host='127.0.0.1', port= '5432')
#Open cursor
cursor = conn.cursor()
#Execute Cursor
cursor.execute("select datname from

Select
import psycopg2
conn = psycopg2.connect(database = "postgres",
user = "postgres", password = "postgres", host =
"127.0.0.1", port = "5432")
cursor = conn.cursor()
cursor.execute("select * from test2")
data = cursor.fetchone()
cursor.execute("select * from test2")
data = cursor.fetchmany(2)

Create Table
import psycopg2
conn = psycopg2.connect(database =
"postgres", user = "postgres", password =
"postgres", host = "127.0.0.1", port =
"5432")
print ("Opened database successfully")
cur = conn.cursor()
cur.execute('''CREATE TABLE COMPS
(ID INT PRIMARY KEY NOT NULL,

Insert
#CREATE TABLE
- cursor.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer,
data varchar(99));")
- conn.commit
#INSERT/UPDATE RECORD
cursor.execute("INSERT INTO test (num, data) VALUES (%s, %s)",(100,
"sqlnosql.com"))
conn.commit
#UPDATE
cursor.execute("UPDATE test2 set num = 999 where ID = 4")
conn.commit
cursor.rowcount

Python file
Write code in python file
Vi a.py
#Execute
python3 a.py

Contact
Website: www.sqlnosql.com
Email : sachinep84@gmail.com
Linkedin : https://www.linkedin.com/in/sachinep84/

Psycopg2 postgres python DDL Operaytions (select , Insert , update, create table)

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