Update Powerbi_interview_2.md

Author: rritec

03. Interview Questions/Powerbi_interview_2.md

@@ -10,6 +10,26 @@
       "Total Amount",sum(Sales[Sales Amount])
       )
       ```
+- SUMMARIZECOLUMNS:
+    - Create a summary table for the requested totals over set of groups
+    - Syntax: ```SUMMARIZECOLUMNS ( [<GroupBy_ColumnName> [, [<FilterTable>] [, [<Name>] [, [<Expression>] [, <GroupBy_ColumnName> [, [<FilterTable>] [, [<Name>] [, [<Expression>] [, … ] ] ] ] ] ] ] ] ] )```
+    - Example:
+    ``` dax
+--  SUMMARIZECOLUMNS is the primary querying function in DAX
+--  It provides most querying features in a single function:
+--      First set of arguments are the groupby columns
+--      Second set are the filters
+--      Third set are additional columns added to the resultset
+EVALUATE
+SUMMARIZECOLUMNS (
+    'Product'[Brand],
+    'Date'[Calendar Year],
+    TREATAS ( { "CY 2008", "CY 2009" }, 'Date'[Calendar Year] ),
+    TREATAS ( { "Red", "Blue" }, 'Product'[Color] ),
+    "Amount", [Sales Amount],
+    "Qty", SUM ( Sales[Quantity] )
+)
+    ```
 
 
 2.