After my post earlier this week on creating current day/week/month/year reports in Power BI a few people asked me for a more detailed explanation of the way I was creating tables without using a data source in my M code. This is something I find myself doing quite a lot when I’m loading data with Power BI and Power Query, and while there are several ways of doing this I find that using the #table() intrinsic function is the most elegant option.
Let’s look at some examples. The following query returns a table with two columns (called “First Column” and “Second Column”) and two rows containing the values from 1 to 4:
#table({"First Column", "Second Column"}, {{1,2},{3,4}})
No data source is needed – this is a way of defining a table value in pure M code. The first parameter of the function takes a list of column names as text values; the second parameter is a list of lists, where each list in the list contains the values on each row in the table.
In the last example the columns in the table were of the data type Any (the ABC123 icon in each column header tells you this), which means that they can contain values of any data type including numbers, text, dates or even other tables. Here’s an example of this:
#table(
{"First Column", "Second Column"},
{
{1,"Hello"},
{#date(2016,1,1),3}
}
)
While this is flexible it’s not exactly practical: in almost all cases the Any data type is a bad choice for loading data, and you need to explicitly set the data type for each column. You can set data types for columns quite easily as a separate step, but it is also possible to set column data types using #table():
#table(
type table
[
#"Number Column"=number,
#"Text Column"=text,
#"Date Column"=date
],
{
{1,"Hello",#date(2016,1,1)},
{2,"World",#date(2017,12,12)}
}
)
In this example the first parameter is no longer a list of column names but a declaration of a table type that not only has column names in but also column types. You can see from the icons in the column headers in the screenshot above that the column called “Number Column” has a data type of number, “Text Column” has a data type of text, and “Date Column” has a data type of date.
Of course if you need a fixed table value in Power BI you could use the “Enter Data” button or, if you’re using Excel and Power Query you could create an Excel table and then use the Excel.CurrentWorkbook() function to load the contents of it; if you or your end users need to edit the values in your table easily then you should use one of these two options. On the other hand if you don’t want users to be able to edit the values in the table or, more likely, you are generating the contents of your table using functions that return lists (as in my previous post) then #table() is the way to go.
