What are schemas in PostgreSQL used for? Why can't everything be done in public?

Schemas in PostgreSQL are a way to logically separate database objects (tables, views, functions, etc.) within a single database. They allow:

• Organizing objects into groups for easier management.
• Avoiding name conflicts between objects.
• Managing access rights at the schema level.
• Ensuring data isolation and structure.

Using only the public schema is not recommended because:

• All objects will be in one namespace, which complicates support and scaling.
• It is harder to restrict access rights.
• Less flexibility when working with different modules or application components.

Example of creating a schema and a table within it:

CREATE SCHEMA sales;
CREATE TABLE sales.orders (
    id SERIAL PRIMARY KEY,
    amount NUMERIC
);

Thus, schemas help structure the database and manage access more effectively.