Measures And Calculated Columns in DAX .

What is DAX?

Data Analysis Expressions (DAX) can be used to create measures and columns within POWER BI which gives lots of insights of the data. DAX is a collection of functions, operators and constants that can be used in a formula or expression to calculate and return one or more values. It helps you create new information from data already in your model.

MEASURES:

Measures can be seen in table but its not visible in the row or as a separate column. Measures can be used to keep data model small.

To create measure we need to select on new measure and then write a DAX function. For example :

Here , I have created a measure using DAX function for total sales. We can see how it is visible.

Measure won't be visible in table as a separate column . In Measures aggregates has to be explicit. This is the measure value in report view.

In measure we won't have aggregates to select as in calculated column. Here in the image we can see when we select a drop down at measure we won't find any aggregates to select. We actually define the aggregation type in measure.

Here in measure by using aggregation i.e. SUMX, we explicit, but in calculated column we don't explicit.

CALCULATED COLUMNS:

Calculated columns are created whenever we need a column to be replaced with new column. Calculated column will be displayed as a separate column with rows in data model view.

To create a calculated column, we use a new column option from table tools on the top of the Power BI page and write a column name, as we can see in the image.

In columns we can implicitly use aggregation type, here in the image we can see when we select the calculated column in report view on the right side we can see a calculated column then click on the drop down where we can select the aggregates such as average, minimum, maximum, count n so on. Firstly when we just select the column name by default it will show sum aggregation.

For Example:

It has a row context and filters can be used in calculated column. Here we are selecting the customer name column to filter the total sales calculated column. As seen in image.

For example: In earlier image we have seen total sales was 11M and now when we filtered with customer name it gets differ.

Calculated columns can be used to build relationships between two tables and the calculated columns can create relationship from one table to another.

By using calculated columns we can do grouping as well and we can use this column as a filter for total sales calculated column. For example:

FEW DIFFERENCES BETWEEN MEASURES AND CALCULATED COLUMNS:

MEASURE	CALCULATED COLUMN
Measures are not precalculated and doesn't have a separate column. It can be used to keep data model small.	Calculated columns are precalculated as rows and shows as a separate column. It will be added in data model.
As it doesn't understand the row context, to aggregate we need to explicilty define, how thevalues are being aggregated.	It is stored as a row context and implicitly apply aggregates on the reports and select the aggregates as per needed.
As it doesn't have row context, it cannot be used as filters and relationships between tables.	As it has row context, it can be used as filters and relationships between multiple tables.
It cannot be used for grouping, as it needs to have row context.	It can be used for grouping which can be used as filters too.