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POReversing the logic of NHibernate query
 

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  1. POReversing the logic of NHibernate query
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    <p>I have constructed the following query using <code>NHibernate</code> which will give me a collection of <code>MenuView</code> items which contain a given page (referenced by the pages id).</p> <pre><code>// Only retrieve the required properties from Menu object ProjectionList menuViewProjections = Projections.ProjectionList() .Add(Projections.Property("ID"), "ID") .Add(Projections.Property("Name"), "Name") .Add(Projections.Property("Description"), "Description"); var menus = session.CreateCriteria(typeof(Menu)) // Only menu's that are editable .Add(Restrictions.Eq("IsEditable", true)) // Only project required properties .SetProjection(menuViewProjections) // Only menu's that contain this page (Menu object has IList&lt;Page&gt; property called 'Pages') .CreateCriteria("Pages") // Restrict to menu's containing the pages with an id of the specified value .Add(Restrictions.Eq("ID", pageId)) // Transform results into required, light-weight, view objects .SetResultTransformer(Transformers.AliasToBean(typeof(MenuView))) .List&lt;MenuView&gt;(); </code></pre> <p>This works fine; however, now I want to do the opposite: I want to query for all editable menu objects that <strong>do not</strong> contain the page with specified ID. I have thus far not found a solution for this. I would have thought a simple reversal of the pages section of the above query would suffice resulting in:</p> <pre><code>// Only retrieve the required properties from Menu object ProjectionList menuViewProjections = Projections.ProjectionList() .Add(Projections.Property("ID"), "ID") .Add(Projections.Property("Name"), "Name") .Add(Projections.Property("Description"), "Description"); var menus = session.CreateCriteria(typeof(Menu)) // Only menu's that are editable .Add(Restrictions.Eq("IsEditable", true)) // Only project required properties .SetProjection(menuViewProjections) // Only retrieve menus that do NOT contain this referenced page .CreateCriteria("Pages") .Add(Restrictions.Not(Restrictions.Eq("ID", pageId))) // Transform results into required view objects .SetResultTransformer(Transformers.AliasToBean(typeof(MenuView))) .List&lt;MenuView&gt;(); </code></pre> <p>But, this results in the following SQL:</p> <pre><code>SELECT this_.ID as y0_, this_.Name as y1_, this_.Description as y2_ FROM [Menu] this_ inner join PagesInMenu pages3_ on this_.ID = pages3_.MenuID inner join [Page] page1_ on pages3_.PageID = page1_.ID WHERE this_.IsEditable = 1 /* @p0 */ and not (page1_.ID = 8 /* @p1 */) </code></pre> <p>Which is still returning results of Menu items that <strong>do</strong> contain a page with id of 8. Why is this simple reversal of logic not so simple in terms of code?</p> <p><strong>[Update]</strong> Taking on the suggestions from Firo, the suggested query alteration to;</p> <pre><code>// Only retrieve menus that do NOT contain this referenced page .CreateCriteria("Pages") .Add(Subqueries.PropertyNotIn("Id", querymenuItemswithPage)) &lt;--- query you have would be here </code></pre> <p>Now generates the following sql statement;</p> <pre><code> SELECT this_.ID as y0_, this_.Name as y1_, this_.Description as y2_ FROM [Menu] this_ inner join PagesInMenu pages3_ on this_.ID = pages3_.MenuID inner join [Page] page1_ on pages3_.PageID = page1_.ID WHERE this_.IsEditable = 1 /* @p0 */ and page1_.ID not in (SELECT this_0_.ID as y0_ FROM [Page] this_0_ WHERE this_0_.ID = 1 /* @p1 */ </code></pre> <p>)</p> <p>Which at first seems exactly what I wanted but sadly (probably due to my poor understanding of joins) is still not returning quite what I wanted. Given the following tables</p> <p><strong>Menu</strong></p> <p><img src="https://i.stack.imgur.com/6g1nC.png" alt="Shot of menu table"></p> <p>And then the join-table of <strong>PagesInMenu</strong> (with a WHERE clause of WHERE PageID = 1)</p> <p><img src="https://i.stack.imgur.com/jzRPh.png" alt="Show of join table"></p> <p>We can see that page with id of 1 is NOT referenced in menus 5 and 6. I expect the query in question to only return a single row, which would be the ID, Name and Description of Menu with ID of 5 as this is the only menu which page 1 is <strong>not</strong> included in and which <strong>is</strong> editable</p> <p>Instead, the new query returns;</p> <p><img src="https://i.stack.imgur.com/8UEiX.png" alt="enter image description here"></p> <p>I have crossed out all the rows that are returned but shouldnt be. What is going on here !?</p>
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    1. CObecause its a change from "one item in Pages match the condition" to "all items in Pages match the condition"
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