By Rick Copeland
Essential SQLAlchemy introduces a high-level open-source code library that makes it more straightforward for Python programmers to entry relational databases reminiscent of Oracle, DB2, MySQL, PostgreSQL, and SQLite. SQLAlchemy has develop into more and more renowned in view that its liberate, however it nonetheless lacks sturdy offline documentation. This sensible publication fills the distance, and since a developer wrote it, you get an aim examine SQLAlchemy's instruments instead of an advocate's description of the entire "cool" features.
SQLAlchemy comprises either a database server-independent SQL expression language and an object-relational mapper (ORM) that permits you to map "plain previous Python objects" (POPOs) to database tables with out considerably altering your present Python code. Essential SQLAlchemy demonstrates easy methods to use the library to create an easy database program, walks you thru basic queries, and explains the right way to use SQLAlchemy to connect with a number of databases concurrently with an analogous Metadata. you furthermore may learn the way to:
* Create customized kinds for use on your schema, and while it's worthwhile to exploit customized instead of integrated types
* Run queries, updates, and deletes with SQLAlchemy's SQL expression language
* construct an item mapper with SQLAlchemy, and comprehend the variations among this and energetic list styles utilized in different ORMs
* Create gadgets, shop them to a consultation, and flush them to the database
* Use SQLAlchemy to version item orientated inheritance
* supply a declarative, energetic checklist trend to be used with SQLAlchemy utilizing the Elixir extension
* Use the SQLSoup extension to supply an automated metadata and item version in line with database reflection
In addition, you'll find out how and whilst to exploit different extensions to SQLAlchemy, together with AssociationProxy, OrderingList, and more.
Essential SQLAlchemy is the much-needed consultant for each Python developer utilizing this code library. rather than a feature-by-feature documentation, this booklet takes an "essentials" strategy that offers you precisely what you must turn into efficient with SQLAlchemy correct away.
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Additional info for Essential SQLAlchemy
50 ... , display_name=? id = ... 50 ['password1', 'Michael', 4] To delete an object, simply call the session’s delete( ) method with the object to be deleted. commit() 30 | Chapter 2: Getting Started 2007-09-09 ... DELETE 2007-09-09 ...  2007-09-09 ... id = ? 50 The SQLAlchemy ORM also includes support for managing relationships between classes, as well as flexible overrides of its column-mapping conventions. The ORM is covered in more detail in Chapters 6, 7, 8. SQLAlchemy Tutorial | 31 CHAPTER 3 Engines and MetaData This chapter introduces SQLAlchemy’s Engine and MetaData classes.
Reflect( bind=None, schema=None, only=None) takes the following arguments: bind A Connectable used to access the database; required only when the MetaData is unbound. The default is None. schema Specifies an alternate schema from which to reflect tables. The default is None. only Directs the MetaData to load only a subset of the available tables. This can be specified either as a sequence of the names to be loaded or as a boolean callable that will be called for each available table with the parameters only( metadata, table name).
If not None, any columns omitted from the list will not be represented on the reflected Table object. In **kwargs, the default is None. mustexist Indicates that the table must already be defined elsewhere in the Python application (as part of this MetaData). An exception is raised if this is not true. In **kwargs, the default is False. useexisting Directs SQLAlchemy to use the previous Table definition for this table name if it exists elsewhere in the application. ) in **kwargs, the default is False.