Common Relationship Operators In this chapter, we will discuss about the operators which build on relationships. __eq__() The above operator is a many-to-one “equals” comparison. The line of code for this operator is as shown below − s = session.query(Customer).filter(Invoice.invno.__eq__(12)) The equivalent SQL query for the above line of code is − SELECT customers.id AS […]
Category Archives: sqlalchemy
SQLAlchemy ORM – Eager Loading Eager load reduces the number of queries. SQLAlchemy offers eager loading functions invoked via query options which give additional instructions to the Query. These options determine how to load various attributes via the Query.options() method. Subquery Load We want that Customer.invoices should load eagerly. The orm.subqueryload() option gives a second […]
SQLAlchemy – Dialects SQLAlchemy uses system of dialects to communicate with various types of databases. Each database has a corresponding DBAPI wrapper. All dialects require that an appropriate DBAPI driver is installed. Following dialects are included in SQLAlchemy API − Firebird Microsoft SQL Server MySQL Oracle PostgreSQL SQL Sybase An Engine object based on a […]