About the Historian Database Tables
The Historian database tables contain read-only data from the Historian archive. This chapter describes the columns contained in the Historian OLE DB Provider tables:
- ihTags Table
- ihArchives Table
- ihCollectors Table
- ihMessages Table
- ihRawData Table
- ihComments Table
- ihTrend Table
- ihQuerySettings Table
- ihCalculationDependencies Table
- ihAlarms Table
- ihEnumeratedSets Table
- ihEnumeratedStates Table
- ihUserDefinedTypes Table
- ihFields Table
You cannot perform writes or updates to data in these tables. Almost all columns in Historian OLE DB Provider tables support comparison operators except for the following:
SamplingMode
Direction
NumberOfSamples
IntervalMilliseconds
CalculationMode
FilterTag
FilterMode
FilterComparisonMode
FilterValue
FilterExpression
TimeZone
DaylightSavingTime
RowCount
These columns only support the =
comparison operator.
Nulls are not supported in any column. A blank space is returned when there is no value supplied by the Historian server, instead of a Null
field.