What do you need to know about SQLAlchemy?

What do you need to know about SQLAlchemy?

SQLAlchemy is a popular SQL toolkit and Object Relational Mapper. It is written in Python and gives full power and flexibility of SQL to an application developer. It is an open source and cross-platform software released under MIT license. SQLAlchemy is famous for its object-relational mapper (ORM),…

Is the children collection writeable in SQLAlchemy?

Above, the children collection is fully writeable, and changes to it will be persisted to the database as well as locally available for reading at the time they are added. However when instances of MyClass are freshly loaded from the database, the children collection stays empty.

When does SQLAlchemy not recognize a reverse relationship?

If there is a relationship() from Parent to Child, but there is not a reverse-relationship that links a particular Child to each Parent, SQLAlchemy will not have any awareness that when deleting this particular Child object, it needs to maintain the “secondary” table that links it to the Parent. No delete of the “secondary” table will occur.

Do you need bidirectional relationship in SQLAlchemy?

Note that this relationship does not need to be bidirectional; SQLAlchemy is strictly looking at every relationship () associated with the Child object being deleted. A higher performing option here is to use ON DELETE CASCADE directives with the foreign keys used by the database.

https://www.youtube.com/watch?v=OvhoYbjtiKc

SQLAlchemy provides abstractions for most common database data types, and a mechanism for specifying your own custom data types. The methods and attributes of type objects are rarely used directly.

How does SQLAlchemy choose the best column type?

SQLAlchemy will choose the best database column type available on the target database when issuing a CREATE TABLE statement. For complete control over which column type is emitted in CREATE TABLE, such as VARCHAR see SQL Standard and Multiple Vendor Types and the other sections of this chapter. A type for bigger int integers.

Is the uniqueconstraint flag supported in SQLAlchemy?

SQLAlchemy supports both the Index construct with the flag unique=True, indicating a UNIQUE index, as well as the UniqueConstraint construct, representing a UNIQUE constraint. Both objects/syntaxes are supported by MySQL when emitting DDL to create these constraints.

When to use integer and string in SQLAlchemy?

SQLAlchemy will use the Integer and String(32) type information when issuing a CREATE TABLE statement and will use it again when reading back rows SELECTed from the database. Functions that accept a type (such as Column()) will typically accept a type class or instance; Integer is equivalent to Integer() with no construction arguments in this case.