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POWhy is ORM considered good but "select *" considered bad?
 

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  1. POWhy is ORM considered good but "select *" considered bad?
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    <p>Doesn't an ORM usually involve doing something like a select *?</p> <p>If I have a table, MyThing, with column A, B, C, D, etc, then there typically would be an object, MyThing with properties A, B, C, D. </p> <p>It would be evil if that object were incompletely instantiated by a select statement that looked like this, only fetching the A, B, not the C, D:</p> <p>select A, B from MyThing /* don't get C and D, because we don't need them */</p> <p>but it would also be evil to always do this:</p> <p>select A, B, C, D /* get all the columns so that we can completely instantiate the MyThing object */</p> <p>Does ORM make an assumption that database access is so fast now you don't have to worry about it and so you can always fetch all the columns?</p> <p>Or, do you have different MyThing objects, one for each combo of columns that might happen to be in a select statement?</p> <p><strong>EDIT: Before you answer the question, please read Nicholas Piasecki's and Bill Karwin's answers. I guess I asked my question poorly because many misunderstood it, but Nicholas understood it 100%. Like him, I'm interested in other answers.</strong></p> <hr> <p>EDIT #2: Links that relate to this question:</p> <p><a href="https://stackoverflow.com/questions/18655/why-do-we-need-entity-objects">Why do we need entity objects?</a></p> <p><a href="http://blogs.tedneward.com/2006/06/26/The+Vietnam+Of+Computer+Science.aspx" rel="nofollow noreferrer">http://blogs.tedneward.com/2006/06/26/The+Vietnam+Of+Computer+Science.aspx</a>, especially the section "The Partial-Object Problem and the Load-Time Paradox"</p> <p><a href="http://groups.google.com/group/comp.object/browse_thread/thread/853fca22ded31c00/99f41d57f195f48b" rel="nofollow noreferrer">http://groups.google.com/group/comp.object/browse_thread/thread/853fca22ded31c00/99f41d57f195f48b</a>?</p> <p><a href="http://www.martinfowler.com/bliki/AnemicDomainModel.html" rel="nofollow noreferrer">http://www.martinfowler.com/bliki/AnemicDomainModel.html</a></p> <p><a href="http://database-programmer.blogspot.com/2008/06/why-i-do-not-use-orm.html" rel="nofollow noreferrer">http://database-programmer.blogspot.com/2008/06/why-i-do-not-use-orm.html</a></p>
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    1. USCorey Trager
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    1. COperhaps the problem is the title - "select *" instead of "select x,y,z" ?
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    2. COWhich ORM are you using which does a SELECT *? I have used llblgen and nhibernate, both spell out every column to fetch
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