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.