Question

differentiate between fetchone and fetchall with suitable example​

Answer 1

Answer:

they been designed to encourage and maintain similarity between the Python modules that are used to access databases. So it doesn’t matter which database you use. Be it MySQL, PostgreSQL and SQLite syntax the syntax of functions and the way of accessing the relational database is the same in all database modules.We generally use the following Python module to work with Database.

Database Module

MySQL MySQL Connector Python

PostgreSQL Psycopg2

SQLite sqlite3

Above all, interfaces or modules are adhere to Python Database API Specification v2.0 (PEP 249). In this article, I will show how to use fetchall, fetchmany(), fetchone() to retrieve data from MySQL, PostgreSQL, SQLite database.

Before proceeding further first understand what is the use of fetchall, fetchmany(), fetchone().

cursor.fetchall() fetches all the rows of a query result. It returns all the rows as a list of tuples. An empty list is returned if there is no record to fetch.

cursor.fetchmany(size) returns the number of rows specified by size argument. When called repeatedly this method fetches the next set of rows of a query result and returns a list of tuples. If no more rows are available, it returns an empty list.

cursor.fetchone() method returns a single record or None if no more rows are available.

I have created a database_developers table in my database. Now, it contains five rows. let see how to use fetchall to fetch all the records.

the example is in the above of the page

Answer 2

fetchall() fetches all the rows of a query result. An empty list is returned if there is no record to fetch the cursor.

fetchone() method returns one row or a single record at a time. It will return None if no more  rows / records are available.

Any example to be given.