Free Analytics-DA-201 flashcards

When DATEDIFF uses the 'month' part, what exactly does it count between two dates, and why can that over-count complete elapsed months?

DATEDIFF('month', start, end) counts how many times a calendar-month boundary is crossed between the dates, ignoring the day component. So 15 January to 14 March reports two even though only one full month has elapsed. To get complete elapsed months, subtract one whenever the end day has not yet reached the start day.

To count complete months subscribed, write DATEDIFF('month', [Cancel Date], [Signup Date]) minus the day adjustment.

The day-adjustment is correct, but the two date arguments are reversed. DATEDIFF returns a negative value for any customer who cancels after signing up. The arguments must run start then end.

Why is a dual-axis chart the right choice when plotting two measures whose scales differ greatly in one view?

A dual-axis chart synchronises two measures over the same dimension while giving each its own independently scaled vertical axis, so a large currency value and a small percentage stay legible together instead of one swamping the other.

Can a single-axis line chart drawing both measures against the same scale show revenue and margin clearly?

Drawing both on one axis is the natural first attempt, but the percentage line would be flattened against the much larger revenue scale, defeating the comparison.

When offline access and fast in-memory querying matter more than real-time freshness, should you choose an extract or a live connection?

An extract. It materialises the source into a local, compressed, columnar store queried in memory, so it serves analysis offline and reduces repeated load on a source that throttles live reads.

A live connection works for offline analysts because every interaction simply reflects the database's current real-time state.

Tempting because live connections do show current data, but a live connection sends a query to the source on every interaction. That fails the offline requirement and worsens the throttling the team is trying to avoid.

Why must a workbook built on a local Excel file include an extract before publishing it to Tableau Cloud for others to view?

A local file connection is only resolvable from the authoring machine. An extract embeds a snapshot of the data inside the published workbook, so the data resides on Tableau Cloud and stays available to all viewers independent of the author's device.

Can you just publish the workbook with a live connection to the local Excel file path so colleagues can view it?

Tempting because nothing seems to need changing, but a live connection to a local file path is only reachable from the analyst's own machine. Colleagues on Tableau Cloud would see an error when the laptop is off, which is the very problem being avoided.