Add Power BI modeling skill

2026-02-23 20:05:12 +00:00 · 2026-02-03 12:29:33 +03:00
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+# DAX Measures and Naming Conventions
+
+## Naming Conventions
+
+### General Rules
+- Use human-readable names (spaces allowed)
+- Be descriptive: `Total Sales Amount` not `TSA`
+- Avoid abbreviations unless universally understood
+- Use consistent capitalization (Title Case recommended)
+- Avoid special characters except spaces
+
+### Table Naming
+| Type | Convention | Example |
+|------|------------|---------|
+| Dimension | Singular noun | Customer, Product, Date |
+| Fact | Business process | Sales, Orders, Inventory |
+| Bridge | Combined names | CustomerAccount, ProductCategory |
+| Measure Table | Underscore prefix | _Measures, _KPIs |
+
+### Column Naming
+| Type | Convention | Example |
+|------|------------|---------|
+| Keys | Suffix with "Key" or "ID" | CustomerKey, ProductID |
+| Dates | Suffix with "Date" | OrderDate, ShipDate |
+| Amounts | Descriptive with unit hint | SalesAmount, QuantitySold |
+| Flags | Prefix with "Is" or "Has" | IsActive, HasDiscount |
+
+### Measure Naming
+| Type | Convention | Example |
+|------|------------|---------|
+| Aggregations | Verb + Noun | Total Sales, Count of Orders |
+| Ratios | X per Y or X Rate | Sales per Customer, Conversion Rate |
+| Time Intelligence | Period + Metric | YTD Sales, PY Total Sales |
+| Comparisons | Metric + vs + Baseline | Sales vs Budget, Growth vs PY |
+
+## Explicit vs Implicit Measures
+
+### Always Create Explicit Measures For:
+1. Key business metrics users will query
+2. Complex calculations with filter manipulation
+3. Measures used in MDX (Excel PivotTables)
+4. Controlled aggregation (prevent sum of averages)
+
+### Implicit Measures (Column Aggregations)
+- Acceptable for simple exploration
+- Set correct SummarizeBy property:
+  - Amounts: Sum
+  - Keys/IDs: None (Do Not Summarize)
+  - Rates/Prices: None or Average
+
+## Measure Patterns
+
+### Basic Aggregations
+```dax
+Total Sales = SUM(Sales[SalesAmount])
+Order Count = COUNTROWS(Sales)
+Average Order Value = DIVIDE([Total Sales], [Order Count])
+Distinct Customers = DISTINCTCOUNT(Sales[CustomerKey])
+```
+
+### Time Intelligence (Requires Date Table)
+```dax
+YTD Sales = TOTALYTD([Total Sales], 'Date'[Date])
+MTD Sales = TOTALMTD([Total Sales], 'Date'[Date])
+PY Sales = CALCULATE([Total Sales], SAMEPERIODLASTYEAR('Date'[Date]))
+YoY Growth = DIVIDE([Total Sales] - [PY Sales], [PY Sales])
+```
+
+### Percentage Calculations
+```dax
+Sales % of Total = 
+DIVIDE(
+    [Total Sales],
+    CALCULATE([Total Sales], REMOVEFILTERS(Product))
+)
+
+Margin % = DIVIDE([Gross Profit], [Total Sales])
+```
+
+### Running Totals
+```dax
+Running Total = 
+CALCULATE(
+    [Total Sales],
+    FILTER(
+        ALL('Date'),
+        'Date'[Date] <= MAX('Date'[Date])
+    )
+)
+```
+
+## Column References
+
+### Best Practice: Always Qualify Column Names
+```dax
+// GOOD - Fully qualified
+Sales Amount = SUM(Sales[SalesAmount])
+
+// BAD - Unqualified (can cause ambiguity)
+Sales Amount = SUM([SalesAmount])
+```
+
+### Measure References: Never Qualify
+```dax
+// GOOD - Unqualified measure
+YTD Sales = TOTALYTD([Total Sales], 'Date'[Date])
+
+// BAD - Qualified measure (breaks if home table changes)
+YTD Sales = TOTALYTD(Sales[Total Sales], 'Date'[Date])
+```
+
+## Documentation
+
+### Measure Descriptions
+Always add descriptions explaining:
+- What the measure calculates
+- Business context/usage
+- Any important assumptions
+
+```
+measure_operations(
+  operation: "Update",
+  definitions: [{
+    name: "Total Sales",
+    tableName: "Sales",
+    description: "Sum of all completed sales transactions. Excludes returns and cancelled orders."
+  }]
+)
+```
+
+### Format Strings
+| Data Type | Format String | Example Output |
+|-----------|---------------|----------------|
+| Currency | $#,##0.00 | $1,234.56 |
+| Percentage | 0.0% | 12.3% |
+| Whole Number | #,##0 | 1,234 |
+| Decimal | #,##0.00 | 1,234.56 |
+
+## Display Folders
+
+Organize measures into logical groups:
+```
+measure_operations(
+  operation: "Update",
+  definitions: [{
+    name: "YTD Sales",
+    tableName: "_Measures",
+    displayFolder: "Time Intelligence\\Year"
+  }]
+)
+```
+
+Common folder structure:
+```
+_Measures
+├── Sales
+│   ├── Total Sales
+│   └── Average Sale
+├── Time Intelligence
+│   ├── Year
+│   │   ├── YTD Sales
+│   │   └── PY Sales
+│   └── Month
+│       └── MTD Sales
+└── Ratios
+    ├── Margin %
+    └── Conversion Rate
+```
+
+## Variables for Performance
+
+Use variables to:
+- Avoid recalculating the same expression
+- Improve readability
+- Enable debugging
+
+```dax
+Gross Margin % = 
+VAR TotalSales = [Total Sales]
+VAR TotalCost = [Total Cost]
+VAR GrossProfit = TotalSales - TotalCost
+RETURN
+    DIVIDE(GrossProfit, TotalSales)
+```
+
+## Validation Checklist
+
+- [ ] All key business metrics have explicit measures
+- [ ] Measures have clear, descriptive names
+- [ ] Measures have descriptions
+- [ ] Appropriate format strings applied
+- [ ] Display folders organize related measures
+- [ ] Column references are fully qualified
+- [ ] Measure references are not qualified
+- [ ] Variables used for complex calculations