Forum Discussion
SummarizeColumns() and AddMissingItems()
The reason for this is that "SUMMARIZECOLUMNS cannot be used in a context transition. You could use it in a filter, but you cannot invoke SUMMARIZECOLUMNS in a measure because the measure is often called in a context transition." (From Marco's reply to a comment on this article.)
SUMMARIZECOLUMNS is great for writing DAX queries but if you're writing a measure, then you almost always need to use SUMMARIZE instead.
The reason for this is that "SUMMARIZECOLUMNS cannot be used in a context transition. You could use it in a filter, but you cannot invoke SUMMARIZECOLUMNS in a measure because the measure is often called in a context transition." (From Marco's reply to a comment on this article.)
SUMMARIZECOLUMNS is great for writing DAX queries but if you're writing a measure, then you almost always need to use SUMMARIZE instead.