{"id":2025,"date":"2026-09-16T08:44:40","date_gmt":"2026-09-16T08:44:40","guid":{"rendered":"https:\/\/entri.app\/explore\/?post_type=curriculum&#038;p=2025"},"modified":"2026-09-16T08:44:40","modified_gmt":"2026-09-16T08:44:40","slug":"power-query-m-language","status":"publish","type":"curriculum","link":"https:\/\/entri.app\/explore\/power-bi\/power-query-m-language\/","title":{"rendered":"Power Query M Language"},"content":{"rendered":"<h2>What Is Power Query M Language?<\/h2>\n<p>Power Query M is the formula language behind every transformation in Power Query \u2014 both in Power BI and Excel. Each step you create through the Power Query Editor UI generates an M expression behind the scenes. Learning M lets you write custom transformations, build reusable functions, and handle scenarios the UI cannot.<\/p>\n<h2>Power Query M Formula Language \u2014 Key Characteristics<\/h2>\n<ul>\n<li><b><\/b><strong><b>Case-sensitive: <\/b><\/strong>RowCount is valid; table.rowcount is not.<\/li>\n<li><b><\/b><strong><b>Functional: <\/b><\/strong>M is a functional language \u2014 transformations are chained as function calls, each producing a new value without mutating the original.<\/li>\n<li><b><\/b><strong><b>Let\u2026in structure: <\/b><\/strong>Every query is a &#8216;let&#8217; block defining named steps, ending with an &#8216;in&#8217; clause that returns the final result.<\/li>\n<li><b><\/b><strong><b>Rich type system: <\/b><\/strong>Supports tables, records, lists, numbers, text, dates, durations, and more \u2014 each with dedicated library functions.<\/li>\n<\/ul>\n<h2>Power Query M Language Examples<\/h2>\n<p>Below are common M patterns:<\/p>\n<ul>\n<li><b><\/b><strong><b>Filter rows: <\/b><\/strong>SelectRows(Source, each [Amount] &gt; 100)<\/li>\n<li><b><\/b><strong><b>Add a custom column: <\/b><\/strong>AddColumn(Source, &#8220;Profit&#8221;, each [Revenue] &#8211; [Cost], type number)<\/li>\n<li><b><\/b><strong><b>Group and aggregate: <\/b><\/strong>Group(Source, {&#8220;Region&#8221;}, {{&#8220;TotalSales&#8221;, each List.Sum([Sales]), type number}})<\/li>\n<li><b><\/b><strong><b>Replace values: <\/b><\/strong>ReplaceValue(Source, null, 0, Replacer.ReplaceValue, {&#8220;Amount&#8221;})<\/li>\n<li><b><\/b><strong><b>Custom function: <\/b><\/strong>(inputTable as table) =&gt; Table.SelectRows(inputTable, each [Status] = &#8220;Active&#8221;)<\/li>\n<\/ul>\n<h2>How to Access and Edit M Code in Power BI<\/h2>\n<p>In Power Query Editor, click View \u2192 Advanced Editor to see the full M code for the selected query. You can also view individual step formulas in the formula bar above the data preview. Editing M directly is useful for debugging, optimizing, or writing transformations that the UI doesn&#8217;t support (e.g., custom functions, error handling with try\u2026otherwise, or dynamic query parameters).<\/p>\n<h2>How to Write Power Query M Code \u2014 Step-by-Step Tutorial<\/h2>\n<p>This tutorial introduces you to writing and editing M code directly in the Advanced Editor. You will create a simple custom transformation in about 5 steps and under 10 minutes.<\/p>\n<h3>Steps<\/h3>\n<p><strong><b>Step 1: Open the Advanced Eitor<\/b><\/strong><\/p>\n<p>In Power Query Editor, click View \u2192 Advanced Editor. You will see the full M code for the current query, structured as a let\u2026in block.<\/p>\n<p><strong><b>Step 2: Understand the structure<\/b><\/strong><\/p>\n<p>Each line in the &#8216;let&#8217; block is a named step (e.g., Source, #&#8221;Filtered Rows&#8221;). The &#8216;in&#8217; clause at the bottom names the final step whose result is returned. Steps reference earlier steps by name.<\/p>\n<p><strong><b>Step 3: Add a custom step<\/b><\/strong><\/p>\n<p>After the last step in the &#8216;let&#8217; block, add a new line: CustomStep = Table.AddColumn(PreviousStepName, &#8220;Profit&#8221;, each [Revenue] &#8211; [Cost], type number), replacing PreviousStepName with the actual name of the step above. Update the &#8216;in&#8217; clause to return CustomStep.<\/p>\n<p><strong><b>Step 4: Test and debug<\/b><\/strong><\/p>\n<p>Click Done to apply. If there is a syntax error, Power Query highlights the line. Common issues: missing commas between steps, mismatched parentheses, or referencing a step name that does not exist.<\/p>\n<p><strong><b>Step 5: Use try\u2026otherwise for error handling<\/b><\/strong><\/p>\n<p>Wrap expressions that might fail: try [Column] \/ [Divisor] otherwise null. This prevents a single bad row from breaking the entire query.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What Is Power Query M Language? Power Query M is the formula language behind every transformation in Power Query \u2014 both in Power BI and Excel. Each step you create through the Power Query Editor UI generates an M expression behind the scenes. Learning M lets you write custom transformations, build reusable functions, and handle [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"template":"","meta":{"_acf_changed":false},"curriculum-category":[90,91,132],"custom_linking_tags":[134,133],"class_list":["post-2025","curriculum","type-curriculum","status-publish","hentry","curriculum-category-power-bi","curriculum-category-power-bi-tutorials","curriculum-category-merging-queries","custom_linking_tags-mer","custom_linking_tags-merging-queries"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Power Query M Language<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/entri.app\/explore\/power-bi\/power-query-m-language\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Power Query M Language\" \/>\n<meta property=\"og:description\" content=\"What Is Power Query M Language? 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