What is DAX

Data analysis expression language or Duc's was originally released in power pivot in 2000 and 10 Microsoft it's a functional language that very similar to Excel as you would expect and that was part of the XML tools. It's initial basic function was to allow X-URL users solve more complex business problems. Now not only is daks used in power pivot but it's also the language used in analysis services and in power powerpc so I mentioned that daks is similar to Excel but there are some major differences. Excel works on cell references and ranges of cells. Hell in cell Dock's does not doubt daks works on tables and subsets of tables of data. And this is something that you will see as we move through the course. Now in addition to the suite of X functions that work index daks also has many additional more powerful functions that are not available in Excel. When we say that X is a functional language we mean that the language makes a call to a function which is known index as an expression. The result from this expression can then be used in a call to another function. So if you're familiar with the nesting if statements that are commonly used in Excel you could kind of say it's something similar to that you can nest one with in another. So Doc supports a number of different data types. If it's Portes a few more than Excel actually supports. We have integers which is basically just a whole number. We have decimal which is just a fraction of a number. Now we also have a type of currency and this is a combination of both an integer and a decimal. The date and time is also a combination of integer and decimal boolean. We'll give you a true or false result. A string datatype is text and a binary datatype is an object such as a file or an image Ducs syntax is basically not really that difficult but it does differ to X out. And we mentioned earlier that Ixil works with cell references or ranges but Dock's works with tables and columns with in the table and subsets of tables. Let's look at a simple duck's expression such as equals distinct Kent. And then we have sales on our square brackets. Customer ID now like an X out x always starts with an equal sign after that equals sign. You then call an expression which is a function or a formula. Now in this example we have called the distinct caid expression and this will count all the distinct values of a selected column. The table name is shown next shown there in the quotes and that these quotes can be left out if the table name does not contain any special characters. After this we reference the column in the table. In this example we've selected the customer ID column and the results for this expression will give us the unique customers that we have actually sold to index. There are two types of combinations. There is a calculator column and there is a measure and both have their uses and their benefits. Now it's also very worth bringing up at an early stage that Doc's calculations are carried out in two contexts a world context which is the rows or selected rows of a table and a filter context which is DiVall defined by the filters on a pivot table or on a visualization. Understanding the world filter context is very important when writing Duc's calculations. If you don't take these into consideration you might get the value or the result that you have been expecting. And this becomes especially apparent when your data structure contains multiple tables and multiple relationships. And if you've read any of my other articles or watched any of my Ducs videos this is something I will always mention. Now as we work through this course this is something that we will also continue to build upon.