General Guidelines for Building a Query

Using SQL statements, you can retrieve information from the columns and rows in a specified table or tables. You are only limited by the amount of memory on your system when determining the number of data rows that you can retrieve from a table.

Table 1. Historian Database Tables
Table NameDescription
ihTags TableContains Historian tag configuration information.
ihArchives TableContains Historian archive configuration information, plus performance statistics for each archive.
ihCollectors TableContains configuration and status information for each collector connected to the Historian server.
ihMessages TableContains Historian messages such as alerts, informational topics, and connection information contained in the audit log.
ihRawData TableContains collected data for each tag in the Historian server. It contains not just raw data, but also calculated and interpolated data.
ihComments TableContains the comments associated with the Historian data.
ihTrend TableAnother 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 TableContains a set of parameters that apply to all queries you make in that session, unless overridden by a WHERE clause.
ihCalculationDependenciesContains the calculation dependencies for tags.
ihAlarms TableContains collected alarms and events data.
ihEnumeratedSets TableContains information about enumerated sets.
ihEnumeratedStates TableContains information about enumerated states.
ihUserDefinedTypes TableContains information about user-defined data types.
ihFields TableContains information about fields used in user-defined types.