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What Are "Enumerations", and what is the difference between a "Static Enumeration" and a "Lookup Enumeration"?

An Enumeration is a set of ordinals that map integer values to string values. Think of Enumerations as “Lookups”.

Toolbox-Enumerations.png

For example, in your Historian, you may have an integer tag called “FL001.Product” that changes between 0 and 4.

0 represents an “Idle” state for the Filler, but 1 to 4 represent the various products or brands that your Juice Factory produces:

0 = No Production
1 = Apple
2 = Grape
3 = Orange
4 = Raspberry

There are two types of Enumerations that can be configured:

  1. Static Enumerations
  2. Lookup Enumerations

Note: Enumerations are used in conjunction with Event Attributes

 

Static Enumerations

Toolbox-Enumerations-StaticEnumerations.png

A static enumeration consists of a fixed list of ordinals defined with the following properties:

  • Description
This is the ordinal’s description.
  • Ordinal
This is the integer value that Flow associates with the ordinal’s string “Value”.
  • Value
This is the string value that is mapped by Flow to the ordinal.
   

 

Lookup Enumeration

The Lookup Enumeration type allows you to query a Data Source for ordinal values. For example, you could query a Microsoft SQL database for the ordinal and value pairs. The Lookup Enumeration is dynamic and will change depending on the underlying data source values.

 

Toolbox-Enumerations-LookupEnumerations.png

 

When using the Microsoft SQL data source, your query must return two columns, namely “Ordinal” (integer) and “Value” (string). Your query can contain the following optional placeholders:

  • [Event]
The name of the event that is using this Lookup Enumeration.
  • [Attribute]
The name of the attribute that is using this Lookup Enumeration
  • [Ordinal]
The integer Ordinal returned by the Attribute value query.
  • [Timestamp]
The date and time for which the attribute is evaluated.
   

The following is an example SQL query for a “Lookup” Enumeration:

select Ordinal, Value from Lookup
where Event = ‘[Event]’
and Attribute = ‘[Attribute]’
and Ordinal = [Ordinal]
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