September 2024
Intermediate to advanced
208 pages
4h 41m
Spanish
Content preview from SQLAlchemy Esencial, 2ª Edición
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Capítulo 1. Esquema y tipos
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La primera cosa que debemos hacer es definir qué datos contienen nuestras tablas, cómo se interrelacionan esos datos y cualquier restricción sobre ellos.
En para proporcionar acceso a la base de datos subyacente, SQLAlchemy necesita una representación de las tablas que deben estar presentes en la base de datos. Podemos hacerlo de tres maneras:
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Utilizar objetos definidos por el usuario
Table -
Utilizar clases declarativas que representen tus tablas
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Inferirlos de la base de datos
Este capítulo de se centra en la primera de ellas, ya que es el enfoque que se utiliza con SQLAlchemy Core; trataremos las otras dos opciones en capítulos posteriores, una vez dominados los fundamentos. Los objetos Table contienen una lista de columnas tipificadas y sus atributos, que se asocian a un contenedor de metadatos común. Comenzaremos nuestra exploración de las definiciones de esquemas echando un vistazo a los tipos disponibles para construir tablas en SQLAlchemy.
Tipos
En hay cuatro categorías de tipos que podemos utilizar dentro de SQLAlchemy:
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Genérico
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Norma SQL
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Específico del vendedor
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Definido por el usuario
SQLAlchemy define un gran número de tipos genéricos que se abstraen de los tipos SQL reales soportados por cada base de datos backend. Todos estos tipos están disponibles en el módulo sqlalchemy.types, y por comodidad también ...
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