# Snapshot Dimensions

Date dimensions allow you to associate a metric’s underlying facts with certain events, such as the date an opportunity was created. You can also take snapshots of data at predefined intervals, such as at the end of each day or business week. Snapshots are useful for showing the current value of a metric, how a metric value fluctuates over time, or how the current value of a metric compares with an earlier value of the same metric.

Additionally, snapshots include only a subset of project facts. In order to use date dimensions effectively, you should be familiar with your project’s data and logical data model. See Dates and Times.

Unlike other date dimensions whose attributes often appear along the axes of reports, snapshot date dimensions usually form part of a metric’s definition and are not standalone attributes in report definitions.

For example, the chart below shows a sales pipeline in which deal amounts are broken down by stage for two snapshot dates. By including a snapshot filter within the metric, we can create a visualization that shows how the status of the pipeline at the start of the period (gray area) compares to the current status of the pipeline (red area).

## Filtering for a Snapshot Date within a Metric

Beyond allowing you to peer into the past, snapshots also allow you to approximate the current value of a constantly fluctuating or estimated metric.

For example, suppose a sales organization wants to track its progress towards reaching a quarterly quota. They can do this by defining a metric that returns an up-to-date estimate of the earnings that are expected by quarter’s end. Because the estimate is captured by the most recent snapshot of the data, the metric must include a filtering statement to pinpoint the most recent snapshot date.

To filter for the most recent snapshot date, the sales organization in our example must define a condition where the Snapshot (Date) is equal to another metric that we’ll call Snapshot [EOP] for end of period.

``````SELECT SUM(Amount * Probability) WHERE Snapshot(Date) = Snapshot[EOP] and Status in (Open, Won)
``````

Chronological dates are assigned a numerical identifier. The later (more recent) a date is chronologically, the larger the numerical value it is assigned. (For example, November 17, 2014 corresponds to a larger numerical identifier than November 16, 2014.) So, to pinpoint the largest (most recent) snapshot date, the sales organization defines its Snapshot [EOP] metric as follows:

``````SELECT MAX(SELECT Snapshot(Date) BY <connection_point>) BY ALL OTHER EXCEPT Snapshot(Date) WITHOUT PF
``````

The <connection_point> above is an attribute or set of attributes that uniquely identify the records of a data set (for example, Records of Snapshots).

Creating a separate Snapshot [EOP] metric allows you to add additional MAQL syntax in the future to handle more complex use cases and report types without the need to add complexity to the Expected + Won metric. And if it has been defined as a global metric, Snapshot [EOP] can be reused in filter clauses in other project metrics.