The Database Connectivity Toolset is a great add-on toolkit for LabVIEW, it makes the database operation within LabVIEW so easy that you can operate database even without sound knowledge of database.

I used this toolkit in one of my projects to record the test results of UUTs into MS Access database. I created a save results to database subVI with this toolkit. The subVI looks like this:

It is simple. When the table does not exist, this subVI creates the table and inserts data, when the table exist, the subVI inserts data only. When I call this subVI for the first time, everything is fine. But when I call it again with the same table name and different data especially when the string data in the same column is much longer than the last time, there will be an error. After checked the Access database, I found out that the DB Tools Insert Data VI created the table and formatted every column’s size exactly the same as the initial data set. So, inserting data that longer than the initial will make an error.

The solution is first check if the table exists, then use the DB Tools Create Table VI to create table if table does not exist as in the following diagram:

One of my project needs to save test results to different Access database files for different units to be tested. The database files’ name is automatic generated based on UUT’s serial number. Currently, I’m using the LabVIEW Database Connectivity Toolset, and the default method to access a database file by it is UDL file. The UDL file contains only one static database file and it is quite hard to change it programmly without manually select a database file and click the confirm button.  And it will be a nightmare to create each UDL file for each UUT before the test is taken.

To change the UDL file’s content in LabVIEW programmly is not easy too. Because UDL file  is unicode-formatted, and LabVIEW is quite limited in support to unicode. I had tried several ways to change the database file name in UDL file and save the UDL file to hard disk. And when I open the changed UDL again, I got “File corrupted” message. It seemed that it is not a good way.At last, I had to read the help file of Database Connectivity Toolset word by word to find a way to work round. Wow, I found out that the VI DB Tools Open Connection is a Polymorphic VI that accepts string and file path data types. Just append the Access database file’s path after “Provider=Microsoft.Jet.OLEDB.4.0; Data Source=”, and wire it to connection information connector of DB Tools Open Connection VI, and everything will be OK.  Everything get solved.

It is really a good habit to read the help file carefully.