Data islands, single calendars, and set analysis

Quite often within QlikView applications, it is necessary to use the same selection criteria over a number of fields. For example, you may want to have a date selection, which selects Date Ordered on one chart and Date Received on another chart.

Background

Previously, we mentioned circular references. One way in which these are created is when there is a Date selection in multiple date fields. The multiple dates exist so that we can produce charts, for example, using Date Ordered on one chart and Date Received on another.

We could avoid the circular reference by having two selection boxes, but we could then have the issue that only selected records fit with both selections.

The alterative to this is to use the Data Island approach.

How to do it

The way around this is to have a Data Island, where a table is created with no connections to any other table. Have a look at the following script:

Here, we created a MasterCalendar table using the earliest...