SQLAlchemy Tutorial in Python - GeeksforGeeks (2024)

SQLAlchemy - Mapping Python Classes

SQLAlchemy is a popular Python library that provides a nice API for interacting with databases. One of its key features is the ability to map Python classes to database tables, allowing you to use Python objects to represent rows in a database table. This is known as an "object-relational mapper" (ORM). Types of Mappings in Python Classes In SQLAlc

Python SQLAlchemy - Group_by and return max date

In this article, we are going to see how to use Group_by and return max date SQLAlchemy in Python. Installing SQLAlchemy SQLAlchemy is available via pip install package. pip install sqlalchemy However, if you are using flask you can make use of its own implementation of SQLAlchemy. It can be installed using - pip install flask-sqlalchemyExample Bef

Connecting to SQL Database using SQLAlchemy in Python

In this article, we will see how to connect to an SQL database using SQLAlchemy in Python. To connect to a SQL database using SQLAlchemy we will require the sqlalchemy library installed in our python environment. It can be installed using pip - !pip install sqlalchemyThe create_engine() method of sqlalchemy library takes in the connection URL and r

Connecting PostgreSQL with SQLAlchemy in Python

In this article, we will discuss how to connect PostgreSQL with SQLAlchemy in Python. In order to connect with any Database management system, it is essential to create an engine object, that serves as a central source of connection by providing a connection pool that manages the database connections. This SQLAlchemy engine is a global object which

Python SQLAlchemy - func.count with filter

In this article, we are going to see how to perform filter operation with count function in SQLAlchemy against a PostgreSQL database in python Count with filter operations is performed in different methods using different functions. Such kinds of mathematical operations are database-dependent. In PostgreSQL, the count is performed using a function

Python SQLAlchemy - Write a query where a column contains a substring

In this article, we discussed how to extract the column values containing substring in SQLAlchemy against a PostgreSQL database in python. In SQLAlchemy, generic functions like SUM, MIN, MAX, are invoked like conventional SQL functions using the func attribute. Some common functions used in SQLAlchemy are contains, count, cube, current_date, curren

Python SQLAlchemy - Delete Multiple Rows

In this article, we are going to see how to use the DELETE statement to delete multiple rows in SQLAlchemy against a PostgreSQL database in Python. Creating table for demonstration: Import necessary functions from the SQLAlchemy package. Establish connection with the PostgreSQL database using create_engine() function as shown below, create a table

How to use the IN operator in SQLAlchemy in Python?

In this article, we will see how to use the IN operator using SQLAlchemy in Python. We will cover 2 examples, one each for SQLAchemy Core and ORM layers. In both examples, we will count the number of records present in the category table within the sakila database. The sample data from the table looks like. If you do not have sakila database and wa

Python SQLAlchemy - Update table structure

In this article, we are going to update the structure of the table using the sqlalchemy module. The structure of the table includes name of columns, the datatype of columns, constraints, keys, etc which we are going to update in this post. Installing the requirements: Let us first install the SQLAlchemy module by running the following pip command i

Python SQLAlchemy - Performing union with three queries

In this article, we will see how to perform a union of three queries using SQLAlchemy in Python. Since we are going to use MySQL in this post, we will also install a SQL connector for MySQL in Python. However, none of the code implementations changes with change in the database except for the SQL connectors. pip install pymysqlWe will use the sampl

Bulk Insert to Pandas DataFrame Using SQLAlchemy - Python

Let's start with SQLAlchemy, a Python library that allows communication with databases(MySQL, PostgreSQL etc.) and Python. This library is used as an Object Relational Mapper tool that translates Python classes to tables in relational databases and automatically converts function calls to SQL statements that gives application developers the full po

Bulk insert with SQLAlchemy ORM in Python

In this article, we will see how to insert or add bulk data using SQLAlchemy in Python. SQLAlchemy is among one of the best libraries to establish communication between python and databases. We have used the PostgreSQL database for this article. Create a database for demonstration: CREATE DATABASE TEST; Create a connection to the Postgres database

How to update existing table rows in SQLAlchemy in Python?

In this article, we are going to see how to use the UPDATE statement in SQLAlchemy against a PostgreSQL database in Python. Creating table for demonstration:Import necessary functions from the SQLAlchemy package. Establish connection with the PostgreSQL database using create_engine() function as shown below, create a table called books with columns

Python Falcon - SQLAlchemy Models

Python Falcon is an up-to-date web framework with an adjustable applicative architecture that is oriented to creating high-speed application processes and APIs. Another often implemented pattern is CRUD and interaction with the database can be facilitated with the help of SQLAlchemy for Python. When used with SQLAlchemy, Falcon provides developers

How to Fix 'NoSuchModuleError: Can't Load Plugin: sqlalchemy.dialects.postgres.psycopg2' in Python

SQLAlchemy is a powerful SQL toolkit and Object-Relational Mapping (ORM) library for Python. It facilitates interaction with various databases using Python code. However, while working with SQLAlchemy, developers may encounter the error: NoSuchModuleError: Can't Load Plugin: sqlalchemy.dialects.postgres.psycopg2. This error indicates a problem with

Serialize Python SqlAlchemy result to JSON

Serialization is converting the object into a format that can be easily stored or transmitted, and later reconstructed. In web applications, it can often involve converting the database query results into JSON format. It is a popular format for the data interchange between clients and servers. SQLAlchemy is a widely used Object Relational Mapper (O

Difference between psycopg2 and SQLAlchemy in Python

Comparing SQLAlchemy and psycopg2, the choice between the two is primarily dictated by the project at hand. SQLAlchemy is perfect for the situations when a developer does not only need an ORM to interact with the database, but would also like the comfort of choosing the database type. On the other hand, psycopg2 will suit well for developers who ar

Create a SQL table from Pandas dataframe using SQLAlchemy

In this article, we will discuss how to create a SQL table from Pandas dataframe using SQLAlchemy. As the first steps establish a connection with your existing database, using the create_engine() function of SQLAlchemy. Syntax: from sqlalchemy import create_engine engine = create_engine(dialect+driver://username:password@host:port/database) Explana

Sqlalchemy Core With Text SQL For Date Range

SQLAlchemy Core is a low-level SQL abstraction layer of SQLAlchemy, a popular Python Object Oriented Mapping(ORM) library. It provides a way to interact with relational databases wing python code, allowing developers to write SQL Queries in a more object-oriented manner. SQLAlchemy is a python library that provides a set of tools for working with d

SQLAlchemy - Order By before Group By

In this article, we are going to see how to perform the orderby function before using a groupby function in SQLAlchemy against a PostgreSQL database in Python. PostgreSQL, Group by is performed using a function called groupby(), and order by the operation is performed using orderby(). Usage: func.sum(). func.group_by(), func.sum(), func.order_by()

Read SQL database table into a Pandas DataFrame using SQLAlchemy

To read sql table into a DataFrame using only the table name, without executing any query we use read_sql_table() method in Pandas. This function does not support DBAPI connections. read_sql_table()Syntax : pandas.read_sql_table(table_name, con, schema=None, index_col=None, coerce_float=True, parse_dates=None, columns=None, chunksize=None) Paramete

Sqlalchemy core, insert multiple rows from a tuple instead of dict

SQLAlchemy is a popular Python library used for working with databases. SQLAlchemy provides an Object-Relational Mapping (ORM) layer and a Core layer. The ORM layer allows developers to work with databases using Python objects, while the Core layer provides a lower-level interface for SQL-oriented database work. In this article, we'll explore how t

Group by and count function in SQLAlchemy

In this article, we are going to see how to perform Groupby and count function in SQLAlchemy against a PostgreSQL database in Python. Group by and count operations are performed in different methods using different functions. Such kinds of mathematical operations are database-dependent. In PostgreSQL, Group by is performed using a function called g

Select NULL Values in SQLAlchemy

In this article, we will see how to select NULL values into a PostgreSQL database using SQLAlchemy in Python. For demonstration purposes first, let us create a sample table using SQLAlchemy in PostgreSQL as shown below Creating a table using SQLAlchemy in PostgreSQL:Import necessary functions from SQLAlchemy package.Establish connection with the Po

How to use avg and sum in SQLAlchemy Query?

In this article, we are going to see how to use avg and sum in SQLAlchemy query using Python. Installing SQLAlchemy SQLAlchemy is available via the pip install package. pip install sqlalchemy However, if you are using flask you can make use of its own implementation of SQLAlchemy. It can be installed using - pip install flask-sqlalchemyExample Befo

Returning distinct rows in SQLAlchemy with SQLite

In this article, we are going to see how to return distinct rows in SQLAlchemy with SQLite in Python. Installation SQLAlchemy is available via pip install package. pip install sqlalchemy However, if you are using flask you can make use of its own implementation of SQLAlchemy. It can be installed using - pip install flask-sqlalchemyCreating Database

How to GroupBy and Sum SQL Columns using SQLAlchemy?

In this article, we are going to see how to use GroupBy and Sum in SQLAlchemy. Installing SQLAlchemySQLAlchemy is available via pip install package. pip install sqlalchemyHowever, if you are using a flask you can make use of its own implementation of SQLAlchemy. It can be installed using - pip install flask-sqlalchemy In the examples, we will make

Describing Databases with MetaData - SQLAlchemy

In this article, we are going to see how to describe Databases with MetaData using SQLAlchemy in Python. Database Metadata describes the structure of the database in terms of Python data structures. The database usually consists of Tables and Columns. The Database Metadata serves us in generating SQL queries and Object Relational Mapping. It helps

How To Select Only One Column Using SQLAlchemy?

In this article, we are going to see how to select only one column using SQLAlchemy in Python. SQLAlchemy is a large SQL toolkit with lots of different components. The two largest components are SQLAlchemy Core and SQLAlchemy ORM. The major difference between them is SQLAlchemy Core is a schema-centric model that means everything is treated as a pa