Data retrieval subsystem features

Data Retrieval subsystem features include support for:

• Queries with all tag types
  You can include all tag types in the same query when retrieving from the History table. Any combination of tags can be submitted in a single query.

• Both fixed- and variable-length strings

• FILETIME for time computations
  All internal time computation and manipulation is done using the Win32 FILETIME type. The resolution of FILETIME is 100 nanoseconds.

• Time handled as Universal Time Coordinated
  All times are handled internally as UTC. Conversions to and from local time are handled going in and out of retrieval so the external interface is local time.

• Retrieval of different versions

  Note: If you have an application that uses the older SQL Server datetime format, be aware that some rounding can occur as compared to the newer datetime2 format (for example, 3.3ms vs. 100ns).