orm

问题 How do I join two tables as many-to-one and one-to-many in nHibernate. They both have the same 'PLAN_ID' as the key column. My Database structures pre-existing. Below is the mapping I am using and the error I'm getting: Table: PLANN ( one ) PLAN_ID <-- PRIMARY KEY START_DATE CHECK_CHAR ... Table: PLANN_DOCUMENT ( to many ) PLAN_ID <-- PRIMARY KEY DOC_ID <-- ID to a DOCUMENT table DOC_NAME DOC_TYPE Plann class: public virtual... PlanId, StartDate, CheckChar, PlanStatus, public virtual ISet

问题 It seems use the Fluent API has more flexibility. So I choose the way to follow always use the Fluent API to determine the feature it have in db instead use the annotations to. But here is the problem,I couldn't find the way to set the Minimum length. Is there a method to perform this? And i notice,there are no much topic discuss this way.Is the Fluent API way popular?? Hope we choose the right side. 回答1: This is impossible at the moment with EF. If you really have to set a minimum length,

问题 How do we prevent SQL Implicit Conversions in Dapper? We realized, we were conducting an SQL Implicit conversion, causing an Index Scan and Deadlocks. Dapper parameters are nvarchar, while SQL table columns are varchar. This caused all our sql columns convert into nvarchar. We fixed the issue by going through all our embedded Dapper code and converting columns as cast(@SSN as varchar(9)), cast(@LastName as varcarh(25)), cast(@EmployeeId as varchar(10) There has got to be an easier way, is

问题 How do we prevent SQL Implicit Conversions in Dapper? We realized, we were conducting an SQL Implicit conversion, causing an Index Scan and Deadlocks. Dapper parameters are nvarchar, while SQL table columns are varchar. This caused all our sql columns convert into nvarchar. We fixed the issue by going through all our embedded Dapper code and converting columns as cast(@SSN as varchar(9)), cast(@LastName as varcarh(25)), cast(@EmployeeId as varchar(10) There has got to be an easier way, is

问题 The answer I got from an IRC channel: Sequelize is an ORM that includes some query builder stuff; Knex is just a query builder, not an ORM. ORMs don't actually fit very well in many use cases, it's easy to run up against the limits of what they can express, and end up needing to break your way out of them. But that doesn't really explain the pros and cons of each. I am looking for an explanation, and possibly a simple example (use case) highlighting those similarities / differences. Why would

问题 There seems to be a DapperExtensions project, but there is also a SqlMapperExtensions class in the Dapper project. Is there overlap? Is one preferred over the other? I can't find any documentation on Dapper.Contrib. 回答1: Dapper.Contrib is the assembly name: https://github.com/StackExchange/Dapper/tree/master/Dapper.Contrib SqlMapperExtensions is the static class containing the contrib methods within Dapper.Contrib : https://github.com/StackExchange/Dapper/blob/master/Dapper.Contrib

问题 SQLAlchemy relies on me building ORM classes like this: from sqlalchemy import Column, DateTime, String, Integer, ForeignKey, func from sqlalchemy.orm import relationship, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Department(Base): __tablename__ = 'department' id = Column(Integer, primary_key=True) name = Column(String) Is there a tool/script/program than can do this for me? For instance, in C# I can just drag and drop data items from the

问题 class Customer(models.Model): name = models.CharField(max_length=200) # .. class CustomerTicket(models.Model): customer = models.OneToOneField(Customer) date = models.DateTimeField(auto_now_add=True) # .. I want to query all customers. And, adding for each customer its ticket if it has one in the date range - so I will get the ticket object only if it is in the given date range, otherwise the ticket field would be null. 回答1: Try this: from django.db import models customers = Customer.objects

问题 class Customer(models.Model): name = models.CharField(max_length=200) # .. class CustomerTicket(models.Model): customer = models.OneToOneField(Customer) date = models.DateTimeField(auto_now_add=True) # .. I want to query all customers. And, adding for each customer its ticket if it has one in the date range - so I will get the ticket object only if it is in the given date range, otherwise the ticket field would be null. 回答1: Try this: from django.db import models customers = Customer.objects

问题 I use JPA annotations (Hibernate implementation) to initialize my DB schema. And i follow the article DYNAMIC DATASOURCE ROUTING to implement the dynamic datasource routing class. However, i have two databases (mapped 2 data sources). I set the first data source as defaultTargetDataSource. then start my application. When my application try to access 2nd data source, it tell me the table doesn't exist. It seems AbstractRoutingDataSource only create the table for the default data source but