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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 a DBAPI ?

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 DB-API DB-API definition: - We will sometimes want to interact with our database and use its results in a specific programming language.   - To build web applications or data pipelines in a specific language like (Ruby, Python, Javascript, etc.). - That's where DBAPIs come in. A DB-API:  - A DB-API provides a standard for one programming language (like python) to talk to a relational database server. - Is a low-level library for writing SQL statements that connect to a database.  - Also known as database adapters. - Different DBAPIs exist for every server framework or language + database system. - Database adapters define a standard for using a database (with SQL) and using the results of database queries as input data in the given language. -- Turn a selected (SELECT * from some_table;) list of rows into an array of objects in Javascript for say a NodeJS adapter; or a list of tuples in Python for a Python adapter. Examples across languages and server frameworks: - ...
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Connections and Sessions in TCP/IP

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 Connections and Sessions in TCP/IP TCP/IP is a connection-based protocol: - To start any communication a connection must be arranged. - Open a connection to start communications. - Close a connection to end communications.  - Meaning all communications between parties are arranged over a connection. - A connection is established before any data transmission begins. - Over TCP/IP , we'll always need to establish a connection between clients and servers in order to enable communications.  Moreover: Deliveries over the connection are error-checked, If packets arrive damaged or lost, then they are resent (known as retransmission). It's really important that we continually monitor what connections are opened and closed. between a recipient and sender because the more connection that we have open The more performance-based issues we may run into.  We will always need to establish a connection from a client application to a Postgres server Or MySQL server over TCP/IP in o...
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