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Object Relational Mappers Series - So You Want to Use an ORM Anyway

This is my last post on my series on ORMs.  Even after all of the arguments against an ORM, everyone wants to use them.  It seems like there are always two reasons for this:  1)the lure of keeping developers from learning SQL is just too great 2)the belief that the issues with ORM tools won't happen to me.  In every company I've been involved with, when an ORM was proposed, it was eventually implemented regardless of my protests.

Object Relational Mappers Series - The SELECT * Problem

DBAs have been bitching for years that we should never use SELECT * in our queries (or INSERT INTO statements without a column list).  ORMs, usually by default, violate this principle.  

Object Relational Mappers Series - The N+1 SELECTs Problem

This is the next post on ORMs.  Suppose you have a collection of Category objects, which are really just rows in a Category table.  Each Category has a collection of Products.  It's not uncommon to want a listing of Categories with their Products.  In SQL we would have code that looks something like this:  

FROM Category c JOIN Product p on C.Id = P.CategoryId

This will run fairly fast.  An ORM, however, will likely do something like this:  

Object Relational Mappers Series - Polymorphism Problems

This is the next post on my series on ORMs.  ORM mapping isn't generally complex if the row in the table maps to a simple atomic object in your model.  When there isn't a perfect matching of object to relational model we have some problems.  Polymorphism is an example. 

What Is Polymorphism in the Relational World? 


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