Databases Reference
In-Depth Information
•
Information density
of the field, which indicates the percentage of rows that
contain a non-null value.
•
Subset ratio
, which shows the percentage of all distinct values for a field in
the table compared to all the distinct values for that field in the entire data
model. It is only relevant for key fields since they are present in multiple
tables and do not all share the same value. Subset ratios can be used to easily
spot problems in key field associations. For example, when the combined
total of subset ratios for multiple tables is 100 percent, this may indicate that
there are no matching keys between these tables.
•
Tags
, which show the tags applied to the field. Some of these, such as tags
that indicate if the field is a key field or tags indicating the data type of the
field, are automatically generated. Other tags can be manually applied.
• Optionally, any comment set on the field is also shown.
Table preview
While looking at ratios and such will give us some good insights into the data in our
model, it is sometimes easier to just look at the raw data. By right-clicking on a table
and selecting
Preview
, a preview of the first 1,000 table rows will be shown:
Table viewer menu
The menu of the
Table Viewer
dialog contains some other useful functions:
• The
Export Image
command lets us save a picture of the data model in PNG
or BMP format.
• The structure of the QlikView document can be exported using the
Export
Structure
button. This creates three text files: one for the tables, one for the
fields, and one for the mappings between fields. Of course, these text files can
be loaded back into QlikView for further analysis.
• We can also
Print
a picture of the data model or copy a picture of the data
model to the clipboard using the
Copy Image
button.
