DB Toolbox List tables - does not work properly

Question

Hello All
I have two databases: one "c:\a\aa.mdb" contains some tables inside
second "c:\a\bb.mdb" contains no table.
When I run the list tables command from DB toolbox SEPARATELLY the tables are listed in proper way, i.e. one has tables, second does not.
But when I build a vi which returns the table list, and call it twice the result is wrong. Both database seems to have all tables, even though the second does not contain any tables.
I attachment you will find the packed example.
Two databases with udl files (change if unpacked to different directory than c:\a\).
The vi "two vi tables.vi" shows the problem. It calls "find tables.vi" to return the tables in database.
You can see th
at when DB List tables is called in the main vi it works fine. But when it is called two times inside the loop it returns false results.
Can anybody comment on this.
For those who are afraid of unpacking zip files I enclose pictures.
thank you in advance
Pawel
Attachments:
list_tables.zip ‏36 KB
diagram.gif ‏22 KB
front_pannel.gif ‏37 KB

Answer 1

Pawel,
I apologize for the delayed response to your first question. I am currently working on the problem in order to determine a more permanent solution. These forums are a very important resource for not only helping our customers but also for improving our products!
With regards to your other question I believe the problem is one of data flow programming. Each table creation will take a certain amount of time to complete depending on the size and nature of the rows and columns being inserted. Unless you programmatically control the data flow, the �DB Tools Execute Query.vi� does not necessarily know when each table has been created. Since control is handed off to the database program, the �DB Tools Create Table vi� is forced to wait
until the database program returns control.
To programmatically control the flow of data you would need to use either a case structure with a while loop (suggested) or a sequence structure. These structures are critical in cases where execution of a previous section of code must be completed before subsequent code portions are to execute. I have attached an exaple that may prove useful.
The wait method is actually a good way to time data flow but in this case may not be the best solution if you want your table creations to be dynamic over time (you may be forced to change the wait for larger table creations, for instance). If you know that your table creations will never change then using a wait method may be an acceptable solution.
I hope this information helps out some. If not please post back with some sample code or more detail on your issue. Good Luck!
Craig H.
National Instruments
Attachments:
Create_Table_Example.zip ‏26 KB