The VIs "DB Tools Fetch Recordset Data.vi" and "DB Tool Select Data.vi" of the
Database Connectivity Toolset have the great disadvantage that they are very,
very slow.
National Instrument is aware of this problem and writes in the KnowledgeBase
document ID 28IDHE52 with the title "Why Is the Database Toolset Slow in
Returning Table Data?": (you can find this article under www.ni.com/support):
If you still wish to return the entire contents from a large table at once,
you can use the methods from the example named Read All Data from the
LabVIEW > Examples > database > DatabaseEx.llb. The subVIs used in this
example were written to use the least number of resources and return the
data as a 2D array of strings. Although it is very
efficient, this method of
reading data is not used elsewhere in the Database Connectivity Toolset,
because it has two limitations:
1. The data returned in the Read All Data example is in the form of a 2D
array of strings...
2. The method used in the Read All Data example in unable to interpret NULL
values. If any item in the returned recordset contains a NULL, an error
is returned and no data is read.
This is true, BUT only a slight modification of the "DB Tools Fetch Table
Data.vi" VI, that is used in the "Read All Data" example, make it possible
to avoid these limitations! After this modification this VI returns the same
2D array of database variants as the "DB Tools Fetch Recordset Data.vi" and
"DB Tool Select Data.vi", but is much, much faster!!
Send me an email and I will email the modified version to everybody who is
interested directly.
Robert
