We hope everyone had a safe and happy new year!
The source code in this issue is designed for Visual Basic 4 and 5. With some modifications it should be able to run in VB3 as well.
This issue shows how to determine if a table or query exists in a database. One potential use for this routine is to determine if the end-user has the most recent database. If they don't have the most recent database you can add the missing components.
We are in the middle of development of an application for a client where the client is quite far away. Instead of having to get his data and convert/import it into a new version of the database, we use this routine to help determine if we need to add fields, indexes or other database objects.
In the next several issues we will be introducing a full-blown Visual Basic class to make manipulating these database objects very easy.
Public Function TableOrQueryExists(sDBName As String, sTableName As String) As Boolean
True if the table/query was found, False if it was not.
The below example uses the TableOrQueryExists to demonstrate one way to ensure the database being used is the most recent version. It assumes that two versions of the SALES.MDB file exists. One without the qryShowAllCustomers query and one with. This code could be used to create the query on the file in the SALES.MDB.
Dim sDBName As String
sDBName = "c:\sales\sales.mdb"
If Not TableOrQueryExists(sDBName, "qryShowAllCustomers") Then
MsgBox "The database you are using is not the most recent version."
' or you could automatically add the query here
End If
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A useful performance enhancement if you will be checking several tables/queries at once would be to pass the database object instead of the filename. This would avoid having to open the database several times (which is a time-consuming operation).
In the next issue or two we will introduce a Visual Basic class for adding fields, indexes, queries and other database objects from VB.
That concludes this issue of COTW. We hope you find the source code useful in your development.
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