![]() ![]() ![]() ![]() The class itself is not a database session yet.īut once we create an instance of the SessionLocal class, this instance will be the actual database session. Create a SessionLocal class ¶Įach instance of the SessionLocal class will be a database session. This is to prevent accidentally sharing the same connection for different things (for different requests).īut in FastAPI, using normal functions ( def) more than one thread could interact with the database for the same request, so we need to make SQLite know that it should allow that with connect_args=.Īlso, we will make sure each request gets its own database connection session in a dependency, so there's no need for that default mechanism. In a similar way you could use any other ORM.īy default SQLite will only allow one thread to communicate with it, assuming that each thread would handle an independent request. Here we will see how to work with SQLAlchemy ORM. So, orion_ could be the name (from the name column in the owners table) of this pet's owner.Īnd the ORM will do all the work to get the information from the corresponding table owners when you try to access it from your pet object.Ĭommon ORMs are for example: Django-ORM (part of the Django framework), SQLAlchemy ORM (part of SQLAlchemy, independent of framework) and Peewee (independent of framework), among others. This way, you could also have an attribute orion_cat.owner and the owner would contain the data for this pet's owner, taken from the table owners. These ORMs also have tools to make the connections or relations between tables or entities. And the value of that attribute could be, e.g. With an ORM, you normally create a class that represents a table in a SQL database, each attribute of the class represents a column, with a name and a type.įor example a class Pet could represent a SQL table pets.Īnd each instance object of that class represents a row in the database.įor example an object orion_cat (an instance of Pet) could have an attribute orion_cat.type, for the column type. ORMs ¶įastAPI works with any database and any style of library to talk to the database.Ī common pattern is to use an "ORM": an "object-relational mapping" library.Īn ORM has tools to convert (" map") between objects in code and database tables (" relations"). The FastAPI specific code is as small as always. Notice that most of the code is the standard SQLAlchemy code you would use with any framework. Some also use their own keywords so just keep that in mind.OAuth2 with Password (and hashing), Bearer with JWT tokensĬreate SQLAlchemy models from the Base classĬreate Pydantic models / schemas for reading / returning We pointed out that some functions of the ALTER statement don’t work on specific databases. Depending on the database you’re using will depend on how far its application goes. Whether we are adding, removing, or modifying columns in a table – the ALTER TABLE command has you covered. RENAME column_name TO new_column_name - MySQL, Oracle, PostgreSQL, SQLite, and others For instance, if we use SQL Server with SSMS it will only support its own built in function.ĮXEC sp_rename ‘. The ALTER command only supports renaming columns for certain databases. We can also use a variation of the command if we need to modify a datatype or setting such as NOT NULL to a column.ĪLTER COLUMN TYPE datatype - PostgreSQL In that case we’d need permissions from a database admin. It’s also typical to not have privileges to drop columns. Note: SQLite does not support the dropping of columns. Instead of adding we can also remove unwanted columns from our tables.ĭROP COLUMN - Alter Table Drop Column Syntax We can add either single or multiple columns using the ALTER TABLE ADD column syntax.ĪDD datatype - Alter Table Add Column SyntaxĮxample: Dropping, Modifying, and Renaming Columns Similarly we can also use alter to rename columns. We can also use ALTER to modify an existing column if a change is needed. ![]() The ALTER command is considered part of a DDL statement since it modifies the structure of a table. We can use the ALTER TABLE command to either add or remove columns in SQL. ![]()
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