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SQLAlchemy library for python

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 SQLAlchemy library for python  Introduction: What is 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 open-source and cross-platform software released under MIT license.  SQLAlchemy is famous for its object-relational mapper (ORM), using which classes can be mapped to the database, thereby allowing the object model and database schema to develop in a cleanly decoupled way from the beginning. It is one type of ORM library, AKA an Object-Relational Mapping library, which provides an interface for using object-oriented programming to interact with a database. Other ORM libraries that exist across other languages include popular choices like javascript libraries Sequelize and Bookshelf. js for NodeJS applications, the ruby library ActiveRecord, which is used inside Ruby on Rails, and CakePHP for applications written on PHP, amongst m...
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SQLAlchemy Model.query cheat-sheet

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SQLAlchemy  Model  query-cheat-sheet Query Methods Here are some useful query methods to get to know.  - Select records all() MyModel.query.all() Fetches all records from a table. Returns list of objects. first() MyModel.query.first() Fetches just the first result. Returns object or None. - Filtering filter_by() MyModel.query.filter_by(attr='some value') Similar to SELECT * from ... WHERE filter() Examples: MyModel.query.filter(MyOtherModel.some_attr='some value') OrderItem.query.filter(Product.id=3) Similar to filter_by , but instead, you specify attributes on a given Model.-- -- equals: query.filter(User.name == 'ed') -- not equals: query.filter(User.name != 'ed') LIKE : query.filter(User.name.like('%ed%')) ILIKE (case-insensitive LIKE): query.filter(User.name.ilike('%ed%')) IN: query.filter(User.name.in_(['ed', 'wendy', 'jack'])) NOT IN: query.filter(~User.name.in_(['ed', 'wendy', 'jack...
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What Is Relational Databases

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What Is Relational Databases  Definitions : -   A database is a collection of data. -    A database system is a system for storing collections of data in some organized way. -    It uses a structure that allows us to identify and access data  in relation  to another piece of data in the database. -    Often, data in a relational database is organized into tables. What is a Relational Database Management System (RDBMS)? -    A relational database management system (RDBMS) is a program that allows you to create, update, and administer a relational database. -   Most relational database management systems use the SQL language to access the database. What is SQL? - SQL ( S tructured  Q uery  L anguage) is a programming language used to communicate with data stored in a relational database management system. - Every relational database system (PostgreSQL, SQLite, MySQL, etc) has its own "flavor" of SQL...
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