IT:AD:Breeze.JS:HowTo:Develop Queries [Notes]

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# IT:AD:Breeze.JS:HowTo:Develop Queries #



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<panel title="Summary">

We use an *EntityManager* instance to process *Queries*, in order to retrieve data from the remote service, 
in order to make *entities* that are mergeg into the local cache.


</panel>


## Process ##

The *Query* is built up fluently using terms similar to what you probably already know from [[IT/LINQ/]].


<WRAP tip>
The Predicate takes a small getting used to coming.
</WRAP>

<sxh javascript>
function getAllTodos(includeArchived) {
    var archivedPredicate = new breeze.Predicate("IsArchived", "==", false);;
    var isDonePredicate = new breeze.Predicate("IsDone", "==", true);;
    var comboPredicate = archivedPredicate.and(isDonePredicate);
    
    var query = breeze.EntityQuery
            .from("Todos")
            .where("IsArchived", "==", false);
            .where("IsArchived", op.NotEquals, true)
            //Or use predicate:   .where(archivedPredicate)
            //Or use combinined predicates:  .where(comboPredicate)
            .skip(3*20)
            .take(20)
            .orderBy("CreatedAt")
            .inlineCount()  //cute...returns a count of the items on the server.
            ;

</sxh>

<WRAP important>
Notice how you built up the `where` clause before hand, as composite predicates using `and` and `or`.
</WRAP>




You then send it off and process the async results:

<sxh javascript>
manager.executeQuery(query)
  .then(function(data) {
         products = data.results;        // a page of products beginning with 'C'
         resultsCount = products.length; // 0 <= resultsCount < pageSize
         inlineCount = data.inlineCount; // count of products beginning with 'C'
        });
</sxh>




### More 

See: http://www.breezejs.com/documentation/query-examples


## Resources ##

* http://www.breezejs.com/documentation/querying-depth
* http://www.breezejs.com/documentation/query-examples