Hi everyone in this blog we will see the different DAX that are used to define or use the relationship between two tables. In Power BI there are two type of relationships                 1. One to One  (1:1)                 2. One to Many   (1:*) Now lets look at the DAX functions that we can use with these relationships. USERELATIONSHIP-  Specifies the relationship to be used in a specific calculation as the one that exists between columnName1 and columnName2. Syntax  USERELATIONSHIP(<columnName1>,<columnName2>) Where, columnName1         The name of an existing column, using standard DAX syntax and fully qualified, that usually represents the many side of the relationship to be used; if the arguments are given in reverse order the function will swap them before using them. This argument cannot be an expression. columnName2         The name of an existing column, using standard DAX syntax and fully qualified, that usually represents the one side or lookup side of the relationship to be used; if the arguments are given in reverse order the function will swap them before using them. This argument cannot be an expression. Key Point The function returns no value; the function only enables the indicated relationship for the duration of the calculation. Example = CALCULATE(SUM(ISales[SalesAmount]), USERELATIONSHIP(Sales[ShippingDate], DateTime[Date])) Limitations           USERELATIONSHIP can only be used in functions that take a filter as an argument. USERELATIONSHIP cannot be used when row level security is defined for the table in which the measure is included. RELATED – Returns a related value from another table. Syntax RELATED(<column>) Where, column        – The column that contains the values you want to retrieve. Key Point A single value that is related to the current row. Example FILTER( ‘Sales_USD’, RELATED(‘Territory'[TerritoryCountry])<>”United States”) RELATEDTABLE Evaluates a table expression in a context modified by the given filters. Where, tableName – The name of an existing table using standard DAX syntax. It cannot be an expression. Key Point A table of values. Example = SUMX( RELATEDTABLE(‘Sales_USD’)       , [Amount_USD])  Limitation The RELATEDTETABLE function changes the context in which the data is filtered, and evaluates the expression in the new context that you specify. This function is a shortcut for CALCULATETABLE function with no logical expression. This function is not supported for use in Direct Query mode when used in calculated columns or row-level security (RLS) rules. Hope this helps.

The CALCULATE function in DAX is the magic key for many calculations we can do in PowerPivot. Below is the syntax: CALCULATE( <expression>, <filter1>, <filter2>… ) The expression that we put in the first parameter has to be evaluated to return the result (i.e. a value, not a table). For this reason, the expression is usually an aggregation function like SUM, MIN, MAX, COUNTROWS and so on. This expression is evaluated in a context that is modified by the filters. A key point is that these filters can both enlarge and restrict the current context of evaluation. Let’s try to understand what it means by considering a few examples. The following data model we have imported in PowerPivot named ‘Contract’ & ‘Project’ Scenario 1 Compare Contract & Project data model on YearMonth Column and take sum of multiple records of revenue column of Project data model into Contract data model Project data model has StartYM & StartRevenue Column as shown below And Contract data model has YM column, using Project data model StartYM, StartRevenue columns & Contract data model YM column, here we have derived StartR column with the help of Calculate() DAX function as shown below Formula is =calculate(sum(Project[StartRevenue]),filter(project,Project[StartYM]=Contract[YM])) Scenario 2 Calculate running total of ToDo column in ‘Contract-ToDo’ data model on basis of YearMonth column as shown below Formula is =calculate(sum(‘Contract-ToDo'[ToDo]),filter(‘Contract-ToDo’,’Contract-ToDo'[YearMonth]