concat function in obiee

Method 1.
CONCAT (expression1, expression2)
where:
character_expression Expressions that evaluate to character strings (if numeric you can use CAST function).
For example – CONCAT (‘The year is ‘, CAST(TimeTable.FiscalYear AS CHAR))
Method 2:
CONCAT (expression1 || expression2 || expression3 and so forth)
where:
Very much like the previous one – expressions that evaluate to character strings, separated by the concatenation operator || (double vertical bars).
For example – CONCAT (‘Total is: $’ || SalesFact.TotalSales ||  ‘USD’)

I need to display the store number like prefix of RST :  RST34556 i used below function i solved it.
' RST'  || Cast( "DWH"."".""."Dim_DWH_GEOG_D"."STORENUMBER"  AS CHAR)