quickstart learn dax basics in 30 minutes

Learning nformation you ligence, and DA miliar with creat even if you hav DAX formulas a ecifically on un pts of both calc familiar with th irst step throug alled on your c X is to creat

QuickStart: Learn DAX Basics in 30 Minutes

Owen Duncan

Summary: This QuickStart is for users new to PowerPivot or tabular model projects

authored in SQL Server Data Tools It is meant to give you a quick and easy introduction

on how you can use Data Analysis Expressions (DAX) to solve a number of basic data modeling and analytical problems

Category: Quick Step-By-Step

Applies to: PowerPivot for Excel (all versions), SQL Server 2008 R2, SQL Server 2012 Source: TechNet Wiki ( link to source content )

E-book publication date: May 2012

13 pages

Copyright © 2012 by Microsoft Corporation

All rights reserved No part of the contents of this book may be reproduced or transmitted in any form or by any means without the written permission of the publisher

Microsoft and the trademarks listed at

http://www.microsoft.com/about/legal/en/us/IntellectualProperty/Trademarks/EN-US.aspx are trademarks of the Microsoft group of companies All other marks are property of their respective owners

The example companies, organizations, products, domain names, email addresses, logos, people, places, and events depicted herein are fictitious No association with any real company, organization, product, domain name, email address, logo, person, place, or event is intended or should be inferred

This book expresses the author’s views and opinions The information contained in this book is provided without any express, statutory, or implied warranties Neither the authors, Microsoft Corporation, nor its resellers, or distributors will

be held liable for any damages caused or alleged to be caused either directly or indirectly by this book

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Let’s Begin!

We will frame DAX around three very important fundamental concepts: Syntax, Functions, and Context Of course,

there are other important concepts in DAX, but understanding these three concepts will provide the best foundation

on which to build your DAX skills

Syntax

Before you create your own formulas, let’s take a look at DAX formula syntax Syntax includes the various elements that make up a formula, or more simply, how the formula is written For example, let’s look at a simple DAX formula used to create new data (values) for each row in a calculated column, named Margin, in a FactSales table: (formula text colors are for illustrative purposes only)

This formula’s syntax includes the following elements:

A The equals sign operator (=) indicates the beginning of the formula, and when this formula is calculated it will return a result or value All formulas that calculate a value will begin with an equals sign

B The referenced column [SalesAmount] contains the values we want to subtract from A column reference in a formula is always surrounded by brackets [] Unlike Excel formulas which reference a cell, a DAX formula always references a column

C The subtraction (-) mathematical operator

D The referenced column [TotalCost] contains the values we want to subtract from values in the [SalesAmount] column

When trying to understand how to read a DAX formula, it is often helpful to break down each of the elements into a language you think and speak every day For example, you can read this formula as:

In the FactSales table, for each row in the Margin calculated column, calculate (=) a value by subtracting (-) values in the [TotalCost] column from values in the [SalesAmount] column

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It is very important your formulas have the correct syntax In most cases, if the syntax is not correct, a syntax error will

be returned In other cases, the syntax may be correct, but the values returned might not be what you are expecting PowerPivot (and SQL Server Data Tools) includes IntelliSense; a feature used to create syntactically correct formulas by helping you select the correct elements

Let’s create a simple formula This task will help you further understand formula syntax and how the IntelliSense feature in the formula bar can help you

Task: Create a simple formula for a calculated column

1 If you are not already in the PowerPivot window, in Excel, on the PowerPivot ribbon, click PowerPivot

Window

2 In the PowerPivot window, click the FactSales table (tab)

3 Scroll to the right-most column, and then in the column header, click Add Column

4 Click in the formula bar along the top of the model designer window

Your cursor now appears in the formula bar The formula bar is where you can type a formula for a

calculated column or a measure

Let’s take a moment to look at the three buttons to the left of the formula bar

When the cursor is active in the formula bar, those three buttons become active The leftmost button, the X,

is simply a cancel button Go ahead and click it Your cursor no longer appears in the formula bar, and the cancel button and checkmark button no longer appear Go ahead and click in the formula bar again The cancel button and the checkmark button now reappear This means you are ready to start entering a

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1 In the FactSales table, click in any empty cell in the Calculation Area (also known as the measure grid in the

model designer) This is the area of empty cells just below a table in the PowerPivot window

2 In the formula bar, type the name Previous Quarter Sales:

3 Type an equals sign = to begin the calculation formula

4 Type the first few letters CAL, and then double-click the function you want to use In this formula, you want

to use the CALCULATE function

5 Type an opening parenthesis ( to begin the arguments to be passed to the CALCULATE function

Notice after typing the opening parenthesis, IntelliSense shows you the arguments required for the

CALCULATE function You will learn about arguments in a little bit

6 Type the first few letters of the FactSales table, and then in the dropdown list, double-click FactSales[Sales]

7 Type a comma (,) to specify the first filter, then type, PRE, and then double-click the PREVIOUSQUARTER

function

After selecting the PREVIOUSQUARTER function, another opening parenthesis appears, indicating another argument is required; this time, for the PREVIOUSQUARTER function

8 Type the first few letters Dim, and then double-click DimDate[DateKey]

9 Close both the argument being passed to the PREVIOUSQUARTER function and the CALCULATE function by typing two closing parentheses ))

Your formula should now look like this:

Previous Quarter Sales:=CALCULATE(FactSales[Sales],

PREVIOUSQUARTER(DimDate[DateKey]))

10 C

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You did it!

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Notice the

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