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Data Identification
Every variable stored in Mervis DB is identified by set of keys and values. Combination of of keys and values marked with attribute “IsKey=true” defines unique identification of variable (equivalent to primary key known from SQL world).
Keys
Any string that consists of characters: a-z, A-Z, 0-9, ., _, - can be used as a key. The key must not start with underscore (“_”) character and must not be empty.
Values
Any string that consists of characters: a-z, A-Z, 0-9, ., _, - can be used as a value.
Example of Variable Keys and Values
Key | Value | IsKey | Description |
---|---|---|---|
SoftPlcRtId | “MyRTNumber3025” | True | Unique identification of Mervis RT defined by user |
GUID | 546 | True | Unique identification of Mervis RT variable generated by Mervis IDE |
VariableName | “Outside Temperature” | False | Non-unique variable name defined by user in Mervis IDE |
Recommended Keys and Values
It's recommended to use the following structure of keys and values for new projects and Mervis DB clients.
Key | Value | IsKey | Description |
---|---|---|---|
DataSource | “MyDS” | False | Unique identification of the particular data source |
Root | “MyDsServer1” | True | Unique identification of the particular Mervis DB client. |
Guid | “var546” | True | Unique identification of variable generated by Mervis DB client. |
Level1 | “MyLevel1Id” | False | |
Level2 | “MyLevel2Id” | False | |
Level3 | “MyLevel3Id” | False | |
Level4 | “MyLevel4Id” | False | |
Level5 | “MyLevel5Id” | False | |
Name | “My Variable” | False | |
Unit | “m3” | False |
Example
Key | Value | IsKey | Description |
---|---|---|---|
DataSource | “SCADASystemXY” | False | Unique identification of the particular data source |
Root | “SCADAServer18” | True | Unique identification of the particular Mervis DB client. |
GUID | “aaaaa-bbbbb-ccccc-ddddd-eeeee” | True | Unique identification of variable generated by Mervis DB client. |
Level1 | “SiteNr500” | False | |
Level2 | “Building A” | False | |
Level3 | “Floor 7” | False | |
Level4 | “Room 17” | False | |
Level5 | “SouthEast” | False | |
Name | “Indoor Temperature” | False | |
Unit | “C” | False |