What LEFT / RIGHT / MID does
Extract parts of text values. In Power BI, the key is not only the formula itself but how it behaves with slicers, relationships, visuals and totals.
Syntax or pattern
LEFT(text, num_chars) / RIGHT(text, num_chars) / MID(text, start, num_chars)5 practical business examples
LEFT / RIGHT / MID in a sales report
Show a measure as text for a title or label.
Sales Label = FORMAT([Total Sales], "$#,0")Use FORMAT for labels, not measures you need to chart as numbers.
Join selected products
Display selected products in a title.
Selected Products = CONCATENATEX(VALUES(Products[Product Name]), Products[Product Name], ", ")Useful for dynamic titles and tooltips.
Extract a code prefix
Return the first characters from a code.
Region Code = LEFT(Sales[Order Code], 3)Useful for calculated columns when codes contain meaning.
Check text contains priority
Identify priority tickets.
Priority Flag = IF(CONTAINSSTRING(Tickets[Subject], "urgent"), "Urgent", "Standard")Good for simple text classification.
Create readable KPI label
Combine text and a formatted measure.
KPI Label = "Sales: " & FORMAT([Total Sales], "$#,0")Useful for cards, titles and tooltips.
Common mistakes to avoid
- Using LEFT / RIGHT / MID before checking whether the data model has the right relationships and filter direction.
- Writing one complex measure instead of creating simple base measures first.
- Testing only at the total level and not checking row, category and date contexts.
- Forgetting that slicers, visuals and relationships can all change the filter context.
FAQ
When should I use LEFT / RIGHT / MID in DAX?
Use LEFT / RIGHT / MID when the calculation pattern matches the business question and the result behaves correctly in the current filter context.
Why is my LEFT / RIGHT / MID measure returning the wrong total?
Most total issues come from row context, filter context, relationships, or using a column aggregation where an iterator or CALCULATE pattern is needed.
Can I use this LEFT / RIGHT / MID pattern in a calculated column?
Some patterns work in calculated columns, but most reporting calculations should be measures so they respond to slicers and report filters.