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alguidelines/navpatterns/1-patterns/queries/use-queries-to-replace-nested-loops/index.html
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<li data-nav-id=/welcome/ title=Welcome class=dd-item><a href=/welcome/><b><i class="fas fa-home"></i> </b>Welcome</a><ul></ul></li>
<li data-nav-id=/bcpatterns/ title="BC Patterns" class=dd-item><a href=/bcpatterns/><b><i class="fas fa-clone"></i> </b>BC Patterns</a><ul></ul></li>
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<li data-nav-id=/navpatterns/1-patterns/ title="1. Patterns" class="dd-item parent"><a href=/navpatterns/1-patterns/>1. Patterns</a><ul>
<li data-nav-id=/navpatterns/1-patterns/activity-log/ title="Activity Logs" class=dd-item><a href=/navpatterns/1-patterns/activity-log/>Activity Logs</a></li>
<li data-nav-id=/navpatterns/1-patterns/argument-table/ title="Argument Table" class=dd-item><a href=/navpatterns/1-patterns/argument-table/>Argument Table</a></li>
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<li data-nav-id=/navpatterns/1-patterns/blocked-entity/data-driven-blocked-entity/ title="Data Driven Blocked Entity" class=dd-item><a href=/navpatterns/1-patterns/blocked-entity/data-driven-blocked-entity/>Data Driven Blocked Entity</a></li></ul></li>
<li data-nav-id=/navpatterns/1-patterns/cached-web-service-calls/ title="Cached Web Server Calls" class=dd-item><a href=/navpatterns/1-patterns/cached-web-service-calls/>Cached Web Server Calls</a></li>
<li data-nav-id=/navpatterns/1-patterns/conditional-cascading-update/ title="Conditional Cascading Update" class=dd-item><a href=/navpatterns/1-patterns/conditional-cascading-update/>Conditional Cascading Update</a></li>
<li data-nav-id=/navpatterns/1-patterns/copy-document/ title="Copy Document" class=dd-item><a href=/navpatterns/1-patterns/copy-document/>Copy Document</a></li>
<li data-nav-id=/navpatterns/1-patterns/create-data-from-templates/ title="Create Data from Templates" class=dd-item><a href=/navpatterns/1-patterns/create-data-from-templates/>Create Data from Templates</a></li>
<li data-nav-id=/navpatterns/1-patterns/create-urls-to-nav-clients/ title="Create URLs to NAV Clients" class=dd-item><a href=/navpatterns/1-patterns/create-urls-to-nav-clients/>Create URLs to NAV Clients</a></li>
<li data-nav-id=/navpatterns/1-patterns/creating-custom-charts/ title="Creating Custom Charts" class=dd-item><a href=/navpatterns/1-patterns/creating-custom-charts/>Creating Custom Charts</a></li>
<li data-nav-id=/navpatterns/1-patterns/cross-session-events/ title="Cross Session Events" class=dd-item><a href=/navpatterns/1-patterns/cross-session-events/>Cross Session Events</a></li>
<li data-nav-id=/navpatterns/1-patterns/currently-active-record/ title="Currently Active Record" class=dd-item><a href=/navpatterns/1-patterns/currently-active-record/>Currently Active Record</a></li>
<li data-nav-id=/navpatterns/1-patterns/data-migration-facade/ title="Data Migration Facade" class=dd-item><a href=/navpatterns/1-patterns/data-migration-facade/>Data Migration Facade</a></li>
<li data-nav-id=/navpatterns/1-patterns/discovery-event/ title="Discovery Event" class=dd-item><a href=/navpatterns/1-patterns/discovery-event/>Discovery Event</a></li>
<li data-nav-id=/navpatterns/1-patterns/document/ title=Document class=dd-item><a href=/navpatterns/1-patterns/document/>Document</a></li>
<li data-nav-id=/navpatterns/1-patterns/easy-update-of-setup-or-supplementary-information/ title="Easy Update Of Setup Or Supplementary Information" class=dd-item><a href=/navpatterns/1-patterns/easy-update-of-setup-or-supplementary-information/>Easy Update Of Setup Or Supplementary Information</a></li>
<li data-nav-id=/navpatterns/1-patterns/error-message-processing/ title="Error Message Processing" class=dd-item><a href=/navpatterns/1-patterns/error-message-processing/>Error Message Processing</a></li>
<li data-nav-id=/navpatterns/1-patterns/extending-the-role-center-headlines/ title="Extending the Role Center Headlines" class=dd-item><a href=/navpatterns/1-patterns/extending-the-role-center-headlines/>Extending the Role Center Headlines</a></li>
<li data-nav-id=/navpatterns/1-patterns/feature-localization-for-data-structures/ title="Feature Localization For Data Structures" class=dd-item><a href=/navpatterns/1-patterns/feature-localization-for-data-structures/>Feature Localization For Data Structures</a></li>
<li data-nav-id=/navpatterns/1-patterns/hooks/ title=Hooks class=dd-item><a href=/navpatterns/1-patterns/hooks/>Hooks</a></li>
<li data-nav-id=/navpatterns/1-patterns/implementation-of-surrogate-keys-using-autoincrement-pattern/ title="Surrogate keys using Autoincrement Pattern" class=dd-item><a href=/navpatterns/1-patterns/implementation-of-surrogate-keys-using-autoincrement-pattern/>Surrogate keys using Autoincrement Pattern</a></li>
<li data-nav-id=/navpatterns/1-patterns/instructions-in-the-ui/ title="Instructions in the UI" class=dd-item><a href=/navpatterns/1-patterns/instructions-in-the-ui/>Instructions in the UI</a></li>
<li data-nav-id=/navpatterns/1-patterns/integration-of-addresses/ title="Integration of Addresses" class=dd-item><a href=/navpatterns/1-patterns/integration-of-addresses/>Integration of Addresses</a></li>
<li data-nav-id=/navpatterns/1-patterns/journal-error-processing/ title="Journal Error Processing" class=dd-item><a href=/navpatterns/1-patterns/journal-error-processing/>Journal Error Processing</a></li>
<li data-nav-id=/navpatterns/1-patterns/journal-template-batch-line/ title="Journal Template Batch Line" class=dd-item><a href=/navpatterns/1-patterns/journal-template-batch-line/>Journal Template Batch Line</a></li>
<li data-nav-id=/navpatterns/1-patterns/master-data/ title="Master Data" class=dd-item><a href=/navpatterns/1-patterns/master-data/>Master Data</a></li>
<li data-nav-id=/navpatterns/1-patterns/multi-file-download/ title="Multi-file Download" class=dd-item><a href=/navpatterns/1-patterns/multi-file-download/>Multi-file Download</a></li>
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<li data-nav-id=/navpatterns/1-patterns/net-exception-handling-in-cal/ title="NET Exception Handling in CAL" class=dd-item><a href=/navpatterns/1-patterns/net-exception-handling-in-cal/>NET Exception Handling in CAL</a><ul>
<li data-nav-id=/navpatterns/1-patterns/net-exception-handling-in-cal/tryfunction-net-exception-handling-in-cal/ title="TryFunction NET Exception Handling in CAL" class=dd-item><a href=/navpatterns/1-patterns/net-exception-handling-in-cal/tryfunction-net-exception-handling-in-cal/>TryFunction NET Exception Handling in CAL</a></li></ul></li>
<li data-nav-id=/navpatterns/1-patterns/no-series/ title="No Series" class=dd-item><a href=/navpatterns/1-patterns/no-series/>No Series</a></li>
<li data-nav-id=/navpatterns/1-patterns/notifications/ title=Notifications class=dd-item><a href=/navpatterns/1-patterns/notifications/>Notifications</a><ul>
<li data-nav-id=/navpatterns/1-patterns/notifications/in-context-notifications/ title="In-context Notifications" class=dd-item><a href=/navpatterns/1-patterns/notifications/in-context-notifications/>In-context Notifications</a></li>
<li data-nav-id=/navpatterns/1-patterns/notifications/notification-lifecycle-management-pattern/ title="Notification Lifecycle Management Pattern" class=dd-item><a href=/navpatterns/1-patterns/notifications/notification-lifecycle-management-pattern/>Notification Lifecycle Management Pattern</a></li></ul></li>
<li data-nav-id=/navpatterns/1-patterns/observer/ title=Observer class=dd-item><a href=/navpatterns/1-patterns/observer/>Observer</a></li>
<li data-nav-id=/navpatterns/1-patterns/posting-routine-select-behavior/ title="Posting Routine - Select Behavior" class=dd-item><a href=/navpatterns/1-patterns/posting-routine-select-behavior/>Posting Routine - Select Behavior</a></li>
<li data-nav-id=/navpatterns/1-patterns/product-name/ title="Product Name" class=dd-item><a href=/navpatterns/1-patterns/product-name/>Product Name</a></li>
<li data-nav-id=/navpatterns/1-patterns/queries/ title=Queries class="dd-item parent"><a href=/navpatterns/1-patterns/queries/>Queries</a><ul>
<li data-nav-id=/navpatterns/1-patterns/queries/select-distinct-with-queries/ title="SELECT DISTINCT with Queries" class=dd-item><a href=/navpatterns/1-patterns/queries/select-distinct-with-queries/>SELECT DISTINCT with Queries</a></li>
<li data-nav-id=/navpatterns/1-patterns/queries/use-queries-to-detect-duplicate-records/ title="use Queries to Detect Duplicate Records" class=dd-item><a href=/navpatterns/1-patterns/queries/use-queries-to-detect-duplicate-records/>use Queries to Detect Duplicate Records</a></li>
<li data-nav-id=/navpatterns/1-patterns/queries/use-queries-to-replace-nested-loops/ title="Use Queries to Replace Nested Loops" class="dd-item active"><a href=/navpatterns/1-patterns/queries/use-queries-to-replace-nested-loops/>Use Queries to Replace Nested Loops</a></li></ul></li>
<li data-nav-id=/navpatterns/1-patterns/read-once-initialization-and-validation/ title="Read-once Initialization and Validation" class=dd-item><a href=/navpatterns/1-patterns/read-once-initialization-and-validation/>Read-once Initialization and Validation</a></li>
<li data-nav-id=/navpatterns/1-patterns/released-entity/ title="Released Entity" class=dd-item><a href=/navpatterns/1-patterns/released-entity/>Released Entity</a></li>
<li data-nav-id=/navpatterns/1-patterns/report-selection/ title="Report Selection" class=dd-item><a href=/navpatterns/1-patterns/report-selection/>Report Selection</a></li>
<li data-nav-id=/navpatterns/1-patterns/security/ title=Security class=dd-item><a href=/navpatterns/1-patterns/security/>Security</a></li>
<li data-nav-id=/navpatterns/1-patterns/setup-specificity-fallback/ title="Setup Specificity Fallback" class=dd-item><a href=/navpatterns/1-patterns/setup-specificity-fallback/>Setup Specificity Fallback</a></li>
<li data-nav-id=/navpatterns/1-patterns/silent-file-upload-and-download/ title="Silent File Upload and Download" class=dd-item><a href=/navpatterns/1-patterns/silent-file-upload-and-download/>Silent File Upload and Download</a></li>
<li data-nav-id=/navpatterns/1-patterns/singleton/ title=Singleton class=dd-item><a href=/navpatterns/1-patterns/singleton/>Singleton</a><ul>
<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-codeunit/ title="Singleton Codeunit" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-codeunit/>Singleton Codeunit</a></li>
<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/ title="Singleton Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/>Singleton Table</a><ul>
<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/cue-table/ title="Cue Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/cue-table/>Cue Table</a></li>
<li data-nav-id=/navpatterns/1-patterns/singleton/singleton-table/setup-table/ title="Setup Table" class=dd-item><a href=/navpatterns/1-patterns/singleton/singleton-table/setup-table/>Setup Table</a></li></ul></li></ul></li>
<li data-nav-id=/navpatterns/1-patterns/standard-journal/ title="Standard Journal" class=dd-item><a href=/navpatterns/1-patterns/standard-journal/>Standard Journal</a></li>
<li data-nav-id=/navpatterns/1-patterns/temporary-dataset-report/ title="Temporary Dataset Report" class=dd-item><a href=/navpatterns/1-patterns/temporary-dataset-report/>Temporary Dataset Report</a></li>
<li data-nav-id=/navpatterns/1-patterns/totals-and-discounts-on-subpages-sales-and-purchases/ title="Totals and Discounts on Subpages Sales and Purchases" class=dd-item><a href=/navpatterns/1-patterns/totals-and-discounts-on-subpages-sales-and-purchases/>Totals and Discounts on Subpages Sales and Purchases</a></li>
<li data-nav-id=/navpatterns/1-patterns/transfer-custom-fields/ title="Transfer Custom Fields" class=dd-item><a href=/navpatterns/1-patterns/transfer-custom-fields/>Transfer Custom Fields</a></li>
<li data-nav-id=/navpatterns/1-patterns/variant-facade/ title="Variant Facade" class=dd-item><a href=/navpatterns/1-patterns/variant-facade/>Variant Facade</a></li></ul></li>
<li data-nav-id=/navpatterns/2-anti-patterns/ title="2. Anti-Patterns" class=dd-item><a href=/navpatterns/2-anti-patterns/>2. Anti-Patterns</a><ul>
<li data-nav-id=/navpatterns/2-anti-patterns/nav-upgrade/ title="Nav Upgrade" class=dd-item><a href=/navpatterns/2-anti-patterns/nav-upgrade/>Nav Upgrade</a></li>
<li data-nav-id=/navpatterns/2-anti-patterns/reusable-bugs/ title="Reusable Bugs" class=dd-item><a href=/navpatterns/2-anti-patterns/reusable-bugs/>Reusable Bugs</a></li></ul></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/ title="3. CAL Coding Guidelines" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/>3. CAL Coding Guidelines</a><ul>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/design/ title=Design class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/design/>Design</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/internally-used-dot-net-types/ title="Internally-used DotNet Types" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/internally-used-dot-net-types/>Internally-used DotNet Types</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/internationalization/ title=Internationalization class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/internationalization/>Internationalization</a><ul>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/internationalization/using-calcdate/ title="Using Calcdate" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/internationalization/using-calcdate/>Using Calcdate</a></li></ul></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/ title=Localizability class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/>Localizability</a><ul>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/captionml-for-system-tables/ title="CaptionML on System Pages" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/captionml-for-system-tables/>CaptionML on System Pages</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/fieldcaption-and-tablecaption/ title="FIELDCAPTION and TABLECAPTION" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/fieldcaption-and-tablecaption/>FIELDCAPTION and TABLECAPTION</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/global-text-constants/ title="Global Text Constants" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/global-text-constants/>Global Text Constants</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/use-text-constants/ title="Use Text Constants" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/use-text-constants/>Use Text Constants</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/localizability/using-optioncaptionml/ title="Using OptionCaptionML" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/localizability/using-optioncaptionml/>Using OptionCaptionML</a></li></ul></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/ title=Readability class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/>Readability</a><ul>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/begin-as-an-afterword/ title="Begin as an 'After Word'" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/begin-as-an-afterword/>Begin as an 'After Word'</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/begin-end/ title="Begin-End - Compound Only" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/begin-end/>Begin-End - Compound Only</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/binary-operator-line-start/ title="Binary Operator to Start Line" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/binary-operator-line-start/>Binary Operator to Start Line</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/blank-lines/ title="Blank Lines.md" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/blank-lines/>Blank Lines.md</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/case-actions/ title="CASE Action" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/case-actions/>CASE Action</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/colon-usage-in-case/ title="Colon usage in CASE" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/colon-usage-in-case/>Colon usage in CASE</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/comments-curly-brackets/ title="Comments inside Curly Brackets" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/comments-curly-brackets/>Comments inside Curly Brackets</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/comments-spacing/ title="Comment Spacing" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/comments-spacing/>Comment Spacing</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/end-else-pair/ title="END ELSE Pair" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/end-else-pair/>END ELSE Pair</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/indentation/ title=Indentation class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/indentation/>Indentation</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/keyword-pairs-indentation/ title="Keyword Pairs - Indentation" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/keyword-pairs-indentation/>Keyword Pairs - Indentation</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/line-start-keywords/ title="Line Start Keywords" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/line-start-keywords/>Line Start Keywords</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/lonely-repeat/ title="Lonely Repeat" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/lonely-repeat/>Lonely Repeat</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/named-invocations/ title="Named Invocations" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/named-invocations/>Named Invocations</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/nested-withs/ title="Nested WITHs" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/nested-withs/>Nested WITHs</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/one-statement-per-line/ title="One Statement Per Line" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/one-statement-per-line/>One Statement Per Line</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/separate-if-and-else/ title="Separate IF and ELSE" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/separate-if-and-else/>Separate IF and ELSE</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/spacing-binary-operators/ title="Spacing Binary Operators" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/spacing-binary-operators/>Spacing Binary Operators</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/spacing-brackets-and/ title="Spacing Brackets and ::" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/spacing-brackets-and/>Spacing Brackets and ::</a></li>
<li data-nav-id=/navpatterns/3-cal-coding-guidelines/readability/spacing-unary-operators/ title="Spacing Unary Operators" class=dd-item><a href=/navpatterns/3-cal-coding-guidelines/readability/spacing-unary-operators/>Spacing Unary Operators</a></li>
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<h1>Use Queries to Replace Nested Loops</h1>
<h4 id=_originally-by-bogdan-sturzoiu-microsoft-development-center-copenhagen_><em>Originally by Bogdan Sturzoiu, Microsoft Development Center Copenhagen</em></h4>
<h2 id=abstract><strong>Abstract</strong></h2>
<p>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.</p>
<h3 id=description><strong>Description</strong></h3>
<p>One of the core operations in a relational database is joining two or more tables. For example, you might need to extract all sales lines in the database together with information regarding the related sales header. This requires joining the Sales Header and Sales Line tables using Sales Header No. as the connecting field.;</p>
<p>The join operation has traditionally been done in C/AL by record looping. When NAV 2013 introduced the query object, it allowed us to produce a data set that is the result of a join operation between two or more tables. This simplifies the problem of finding related records in two tables linked through a foreign key.</p>
<h4 id=pattern-elements><strong>Pattern Elements</strong></h4>
<ol>
<li>Two or more tables that contain records linked through a foreign key: Table 1, Table 2, Table n.</li>
<li>A query object Query X, that joins Table 1, Table 2, etc. based on the connecting key.</li>
<li>A processing codeunit that loops through the query records (or any other code-bearing object).</li>
</ol>
<h4 id=pattern-steps><strong>Pattern Steps</strong></h4>
<ol>
<li>Run the query on the connected tables.</li>
<li>Loop through the records returned by the query.</li>
<li>Process the records.</li>
</ol>
<p><a href=5040.clip_5F00_image002.png><img src=5040.clip_5F00_image002.png alt=" "></a></p>
<p>Figure 1. The pattern elements</p>
<h3 id=usage><strong>Usage</strong></h3>
<h4 id=sample-problem><strong>Sample Problem</strong></h4>
<p>The Bank Acc. Reconciliation Line table (274) and the Bank Account Ledger Entry table (271) are connected through the Bank Account No. field. Identify the matching pairs of records based on having the same remaining amount and transaction date.</p>
<h4 id=solution-using-nested-loops><strong>Solution Using Nested Loops</strong></h4>
<p>The classic C/AL approach is to:</p>
<ol>
<li>
<p>Set the necessary filters on the left table, i.e. table 274.</p>
</li>
<li>
<p>Loop through the filtered records.</p>
</li>
<li>
<p>For each record in the filter, find the related records in the right table (table 271) and set the required filters on it.</p>
</li>
<li>
<p>For each pair of records from the left and right table, decide if they are a solution and if so, apply them to each other.</p>
<p>PROCEDURE MatchSingle@5(BankAccReconciliation@1003 : Record 273);
VAR
BankAccRecLine@1005 : Record 274;
BankAccLedgerEntry@1006 : Record 271;
BankAccEntrySetReconNo@1007 : Codeunit 375;
BEGIN
BankAccRecLine.SETRANGE(&ldquo;Bank Account No.",BankAccReconciliation.&ldquo;Bank Account No.");
BankAccRecLine.SETRANGE(&ldquo;Statement No.",BankAccReconciliation.&ldquo;Statement No.");
BankAccRecLine.SETFILTER(Difference,'&lt;>%1',0);
BankAccRecLine.SETRANGE(Type,BankAccRecLine.Type::&ldquo;Bank Account Ledger Entry&rdquo;);
IF BankAccRecLine.FINDSET THEN
REPEAT
BankAccLedgerEntry.SETRANGE(&ldquo;Bank Account No.",BankAccRecLine.&ldquo;Bank Account No.");
BankAccLedgerEntry.SETRANGE(Open,TRUE);
BankAccLedgerEntry.SETRANGE(&ldquo;Statement Status&rdquo;,BankAccLedgerEntry.&ldquo;Statement Status&rdquo;::Open);
BankAccLedgerEntry.SETFILTER(&ldquo;Remaining Amount&rdquo;,'&lt;>%1',0);
IF BankAccLedgerEntry.FINDSET THEN
REPEAT
IF (BankAccRecLine.Difference = BankAccLedgerEntry.&ldquo;Remaining Amount&rdquo;) AND
(BankAccRecLine.&ldquo;Transaction Date&rdquo; = BankAccLedgerEntry.&ldquo;Posting Date&rdquo;) THEN
BankAccEntrySetReconNo.ApplyEntries(
BankAccRecLine,BankAccLedgerEntry, Relation::&ldquo;One-to-One&rdquo;);
UNTIL BankAccLedgerEntry.NEXT = 0;
UNTIL BankAccRecLine.NEXT = 0;
END;</p>
</li>
</ol>
<p>****<strong>Solution Using Query</strong></p>
<p>The new query-based approach involves:</p>
<ol>
<li>
<p>Define a query that returns the full filtered join of tables 271 and 274.</p>
</li>
<li>
<p>Loop through the records returned by the query.</p>
</li>
<li>
<p>For each query record, decide if it represents a solution and then connect the two table records that formed it through an application.</p>
<p>PROCEDURE MatchSingle@5(BankAccReconciliation@1003 : Record 273);
VAR
BankRecMatchCandidates@1001 : Query 1252;
BankAccEntrySetReconNo@1007 : Codeunit 375;
BEGIN
BankRecMatchCandidates.SETRANGE(Rec_Line_Bank_Account_No,
BankAccReconciliation.&ldquo;Bank Account No.");
BankRecMatchCandidates.SETRANGE(Rec_Line_Statement_No,
BankAccReconciliation.&ldquo;Statement No.");
IF NOT BankRecMatchCandidates.OPEN THEN
EXIT;
WHILE BankRecMatchCandidates.READ DO BEGIN
BankAccLedgerEntry.GET(BankRecMatchCandidates.Entry_No);
BankAccRecLine.GET(BankAccRecLine.&ldquo;Statement Type&rdquo;::&ldquo;Bank Reconciliation&rdquo;,
BankRecMatchCandidates.Rec_Line_Bank_Account_No,
BankRecMatchCandidates.Rec_Line_Statement_No,
BankRecMatchCandidates.Rec_Line_Statement_Line_No);
BankAccEntrySetReconNo.ApplyEntries(BankAccRecLine,BankAccLedgerEntry,
Relation::&ldquo;One-to-One&rdquo;);
END;
END;</p>
</li>
</ol>
<p>where the query 1252 is defined as:</p>
<pre><code>OBJECT Query 1252 Bank Rec. Match Candidates
{
OBJECT-PROPERTIES
{
Date=;
Time=;
Version List=;
}
PROPERTIES
{
}
ELEMENTS
{
{ 1 ; ;DataItem; ;
DataItemTable=Table274;
DataItemTableFilter=Difference=FILTER(&lt;\&gt;0),
Type=FILTER(=Bank Account Ledger Entry) }
{ 2 ;1 ;Column ;Rec\_Line\_Bank\_Account\_No;
DataSource=Bank Account No. }
{ 3 ;1 ;Column ;Rec\_Line\_Statement\_No;
DataSource=Statement No. }
{ 4 ;1 ;Column ;Rec\_Line\_Statement\_Line\_No;
DataSource=Statement Line No. }
{ 5 ;1 ;Column ;Rec\_Line\_Transaction\_Date;
DataSource=Transaction Date }
{ 6 ;1 ;Column ;Rec\_Line\_Difference ;
DataSource=Difference }
{ 7 ;1 ;DataItem; ;
DataItemTable=Table271;
DataItemTableFilter=Remaining Amount=FILTER(&lt;\&gt;0),
Open=CONST(Yes),
Statement Status=FILTER(Open);
DataItemLink=Bank Account No.=Bank\_Acc\_Reconciliation\_Line.&quot;Bank Account o.&quot;,
Remaining Amount=Bank\_Acc\_Reconciliation\_Line.Difference,
Posting Date=Bank\_Acc\_Reconciliation\_Line.&quot;Transaction Date&quot; }
{ 8 ;2 ;Column ; ;
DataSource=Entry No. }
{ 9 ;2 ;Column ;Bank\_Account\_No ;
DataSource=Bank Account No. }
{ 10 ;2 ;Column ; ;
DataSource=Posting Date }
{ 11 ;2 ;Column ; ;
DataSource=Remaining Amount }
{ 12 ;2 ;Column ;Bank\_Ledger\_Entry\_Open;
DataSource=Open }
{ 13 ;2 ;Column ; ;
DataSource=Statement Status }
}
CODE
{
BEGIN
END.
}
</code></pre>
<h4 id=heading></h4>
<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><strong>NAV Specific Examples</strong></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><strong>Ideas for Improvement</strong></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>
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