8.3 Mental Map to Excel / Power BI
| Idea | Excel | Power BI | pandas |
|---|---|---|---|
| Bring manager by store | XLOOKUP | Relationship + related columns | merge |
| Stack months | Copy-paste / Power Query append | Append queries | concat |
We do not re-teach the Excel ribbon or Power BI model view here — open those courses if you need the UI.
Practice task
Create a products table (product_id, category, unit_price). Add product_id to orders and left-merge products. List any order with missing category.
Thodkyaat sangaycha tar (quick recap)
- concat stacks; merge joins on keys
- Prefer left join for fact + dimension; audit NaNs
- Check duplicate keys before merging
Samajla ka? Aata pudhe jaauya data cleaning A–Z in pandas.