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<!doctype html><html lang=en class=no-js><head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1,shrink-to-fit=no"><meta name=generator content="Hugo 0.107.0"><meta name=robots content="index, follow"><link rel="shortcut icon" href=/favicons/favicon.ico><link rel=apple-touch-icon href=/favicons/apple-touch-icon-180x180.png sizes=180x180><link rel=icon type=image/png href=/favicons/favicon-16x16.png sizes=16x16><link rel=icon type=image/png href=/favicons/favicon-32x32.png sizes=32x32><link rel=icon type=image/png href=/favicons/android-36x36.png sizes=36x36><link rel=icon type=image/png href=/favicons/android-48x48.png sizes=48x48><link rel=icon type=image/png href=/favicons/android-72x72.png sizes=72x72><link rel=icon type=image/png href=/favicons/android-96x96.png sizes=96x96><link rel=icon type=image/png href=/favicons/android-144x144.png sizes=144x144><link rel=icon type=image/png href=/favicons/android-192x192.png sizes=192x192><title>Use Queries to Replace Nested Loops | alguidelines.dev - Business Central Design Patterns</title><meta name=description content="Originally by Bogdan Sturzoiu, Microsoft Development Center Copenhagen
<!doctype html><html lang=en class=no-js><head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1,shrink-to-fit=no"><meta name=generator content="Hugo 0.110.0"><meta name=robots content="index, follow"><link rel="shortcut icon" href=/favicons/favicon.ico><link rel=apple-touch-icon href=/favicons/apple-touch-icon-180x180.png sizes=180x180><link rel=icon type=image/png href=/favicons/favicon-16x16.png sizes=16x16><link rel=icon type=image/png href=/favicons/favicon-32x32.png sizes=32x32><link rel=icon type=image/png href=/favicons/android-36x36.png sizes=36x36><link rel=icon type=image/png href=/favicons/android-48x48.png sizes=48x48><link rel=icon type=image/png href=/favicons/android-72x72.png sizes=72x72><link rel=icon type=image/png href=/favicons/android-96x96.png sizes=96x96><link rel=icon type=image/png href=/favicons/android-144x144.png sizes=144x144><link rel=icon type=image/png href=/favicons/android-192x192.png sizes=192x192><title>Use Queries to Replace Nested Loops | alguidelines.dev - Business Central Design Patterns</title><meta name=description content="Originally by Bogdan Sturzoiu, Microsoft Development Center Copenhagen
Abstract
This pattern shows how the new query object type introduced in NAV …"><meta property="og:title" content="Use Queries to Replace Nested Loops"><meta property="og:description" content="Originally by Bogdan Sturzoiu, Microsoft Development Center Copenhagen
Abstract This pattern shows how the new query object type introduced in NAV 2013 allows you to replace costly loops when inspecting data from two or more tables.
@ -118,7 +118,7 @@ Description One of the core operations in a relational database is joining two o
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</span></span></span><span style=display:flex><span><span style=color:#ce5c00;font-weight:700> </span>}<span style=color:#f8f8f8;text-decoration:underline>
</span></span></span></code></pre></div><p>When comparing the two implementations, we notice the following advantages of using a query instead of two loops:Comparison</p><ol><li>A query produces the Cartesian product of tables 1 and 2 faster than by looping through both of them. The advantage grows as there are more tables linked.</li></ol><p>The query object leverages the power of SQL Server (as it basically executes a SQL query directly against the database server), and as such it only requires one trip to the database to fetch the data, instead of getting the related records on the right side of the join one by one.</p><ol><li>A query is scalable in the sense that it allows reusing its definition by applying filters when looping through its dataset. So a generic query can be reused for a variety of purposes just by adapting the filters to the programming need. Duplicating traditional record loops in different functions, on the other side, requires extensive code copy-pasting, which can introduce code defects.</li><li>Using a query only requires one loop, whereas joining two or more tables requires multiple code loops that quickly become difficult to read and follow.</li><li>Queries are easy to create and maintain and generally provide a cleaner design.</li></ol><h3 id=nav-specific-examples>NAV Specific Examples</h3><p>In Microsoft Dynamics NAV 2013 R2, we can see the query object used in the bank account reconciliation matching algorithm. The object is query Bank Rec. Match Candidates query (1252), and it is called by the matching engine in the Match Bank Rec. Lines codeunit (1252).</p><h3 id=ideas-for-improvement>Ideas for Improvement</h3><p>The query object type could be improved to allow the passing of parameters at runtime, or, in general, being built dynamically at runtime. This will remove the need for multiple static definitions of the same base query used in slightly different contexts.</p><div class="text-muted mt-5 pt-3 border-top">Last modified February 24, 2022: <a href=https://github.com/microsoft/alguidelines/commit/5ee0436639455a35835c5ce88241d3fad662ee06>Added tags & categories + cleanup (5ee04366)</a>
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