The Historian Database Tables

The Historian database tables contain read-only data from the Historian archive.

Table Name Description
ihTags Table Contains Historian tag configuration information.
ihArchives Table Contains Historian archive configuration information, plus performance statistics for each archive.
ihCollectors Table Contains configuration and status information for each collector connected to the Historian server.
ihMessages Table Contains Historian messages such as alerts, informational topics, and connection information contained in the audit log.
ihRawData Table Contains collected data for each tag in the Historian server. It contains not just raw data, but also calculated and interpolated data.
ihComments Table Contains the comments associated with the Historian data.
ihTrend Table Another way to look at collected data. Contains a row of data for each unique timestamp. You can use this table to look at your data at a summarized level. You would typically use this table to compare multiple tags with the same timestamp.
ihQuerySettings Table Contains a set of parameters that apply to all queries you make in that session, unless overridden by a WHERE clause.
ihCalculationDependencies Contains the calculation dependencies for tags.
ihAlarms Table Contains collected alarms and events data.
ihEnumeratedSets Table Contains information about enumerated sets.
ihEnumeratedStates Table Contains information about enumerated states.
ihUserDefinedTypes Table Contains information about user-defined data types.
ihFields Table Contains information about fields used in user-defined types.
The following conditions apply when using these tables:
  • You cannot write/update data in these tables.
  • Null values are not supported in any column. A blank space is returned when there is no value provided by the Historian server (instead of a Null field).
  • Almost all columns in these 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.