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

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

• 1.
  PostgreSQL Python 1. psycopg2-binary: PostgreSQL Adaptor 2.DDL Operations 3.DML Operations
• 2.
  Installation  pip installpsycopg2-binary  pip3 install psycopg2-binary
• 3.
  Python Connectors Python Application pymongo sqlite3 mySQL pyscopg2 Python Module/Connector PythonDB API’s Request Response
• 4.
  Steps 1) Create Connectionstring 2) Open connection 3) Open cursor 4) Execute cursor 5) Close Cursor 6) Close Connection
• 5.
  Connection Connection class  Handlesconnection 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
• 6.
  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!
• 7.
  CURSOR  Cursor isClass  Allows Python code to execute PostgreSQL command in a database session  Created by  connection.cursor( ) Method  cursor.execute( ), cursor.fetch( ),cursor.close( )
• 8.
  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
• 9.
  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
• 10.
  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.
• 11.
  Cursor.* Cursor.rowcount This read-only attributewhich 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
• 12.
  DDL/DML OPERATIONS -- CreateTable -- Drop Table -- Insert Record -- Update Record -- Select Record -- Delete Record
• 13.
  List Database #Import library importpsycopg2 #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
• 14.
  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)
• 15.
  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,
• 16.
  Insert #CREATE TABLE - cursor.execute("CREATETABLE 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
• 17.
  Python file Write codein python file Vi a.py #Execute python3 a.py
• 18.
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