Databases Reference
In-Depth Information
Mapping tables are prefixed with the word
Map
so that they are immediately
recognizable as mapping tables. These tables can use technical names, for example,
Map_Manufacturer_Country
.
Temporary tables are tables that are not used in the final data model, they hold
a temporary or intermediate result. We did not yet use any temporary tables in
our examples, but when we use them they are prefixed with
TEMP
. For example,
Temp_Flights
.
Field naming conventions
Like tables that are used in the final data model, field names also have a
business-friendly name. For example,
Aircraft Name
instead of
SSD_NAME
.
As many of these names contain spaces, field names are enclosed in square
brackets by default, even if they do not contain any spaces.
Key fields,
, fields that are used to link tables together, are prefixed with a %
(percentage) sign. For example,
[%Aircraft Type ID]
.
Hiding fields
Key fields can cause confusion in the QlikView frontend.
As these fields are used in multiple tables, they can return
unexpected results when used in an aggregation function. It is
therefore advisable to hide these fields from the frontend view.
There are two variables that can be used to hide fields:
HidePrefix
and
HideSuffix
. The first variable hides all field
names that start with a specific text string and the second one
hides all field names that end with a specific text string.
To hide our key fields, we can add the following statement at
the start of our script:
SET HidePrefix='%';
Measures
, fields that contain amounts, are prefixed with a # (pound or hash) sign.
For example,
[# Total Passengers]
.
Flags
, fields that contain a Yes/No or 1/0 indicator, are prefixed with
a _ (underscore) sign. For example,
[_Flight arrived on time]
.
