Top web applications constantly receive and send a lot of new data, automatically entering them into its database, while the preparation of the requests themselves lies on the shoulders of the programmer. A real web application will require writing many queries in the language SQL… For a more concise presentation of them, they are used – Object-relational mappers or ORM… The advantages and disadvantages that we will talk about in this article.
Object-Relational Mapper (ORM) Is a code library that automates the transfer of data stored in relational database tables to objects that are used in application code.
Why are ORMs useful?
ORMs provide a high-level relational database abstraction that allows a developer to write code Python instead of SQL to create, read, update and delete data and schemas in your database. Developers can use the programming language they want to work with the database instead of writing SQL statements or stored procedures.
For example, without the ORM, a developer would write the following statement SQL to get each row in the USERS table where the zip_code column is 94107:
SELECT * FROM USERS WHERE zip_code=94107;
#Вместо этого эквивалентный запрос ORM Django будет выглядеть как следующий код Python:
users = Users.objects.filter(zip_code=94107)
Ability to write code Python instead of SQL can speed up the development of web applications, especially at the beginning of a project. Potential development speed improvement comes from not having to switch from code Python to write operators SQL with a declarative paradigm.
ORMs also theoretically allow you to switch your application between different relational databases. For example, a developer can use SQLite for local development and MySQL in production.
However, in practice, it is better to use the same database for local development as in production. Otherwise, the production environment may experience unexpected errors that were not present in the local development environment. In addition, a project rarely switches from one production database to another, unless there is a good reason.
Access to the database via Python ORM can be carried out both within the framework of the corresponding frameworks Django, Flask, Tornadoand at a low level using connector libraries… Connectors can come in handy when a script involves accessing a database, psycopg (for PostgreSQL) or MySQL-python (for MySQL).
Of course, similar abstractions SQL queries, affect performance when it comes to large amounts of data, which does a good job DBMS… Wherein ORM handles queries well on a small portion of the relational database. The possibility object representation of queries and relational database data solves the problem of minimizing errors in the program code.
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