ACC97: Action Query Commits Changes to Data When Cancelled

MORE INFORMATION

The UseTransaction property specifies whether an action query runs as a single transaction. When the UseTransaction property is set to Yes, the query results are stored in a cache or temporary database and are not written into the current database until you confirm that you want to commit the changes. When the UseTransaction property is set to No, the results are written immediately to the current database; the query runs much faster because it is not wrapped in a single transaction. However, you cannot cancel the changes that the query has made, even if you click No when prompted to commit the changes.

If you create a query in the Microsoft Access user interface by opening a new query in Design view, the default value of the UseTransaction property is Yes. However, when you use data access objects (DAO) to create a QueryDef in Visual Basic for Applications code, the default value of the UseTransaction property is No.

In the following example, the procedure CreateTransQuery creates an actionquery whose UseTransaction property is set to Yes:

1. Open the sample database Northwind.mdb.
2. Create a module and type the following line in the Declarations section if it is not already there:
   

         Option Explicit
   						

3. Type the following procedure:
   

         Function CreateTransQuery()
   
            Dim db As Database
            Dim qd As QueryDef
            Dim prpUseTrans As Property
            Dim strSQLString As String
   
            strSQLString = "UPDATE Categories SET Categories.CategoryName"
            strSQLString = strSQLString & " = 'Drinks' WHERE"
            strSQLString = strSQLString & " Categories.CategoryID = 1;"
            Set db = CurrentDb
            Set qd = db.CreateQueryDef("qryUseTransTest", strSQLString)
            Set prpUseTrans = qd.CreateProperty("UseTransaction", _
               dbBoolean, True)
            qd.Properties.Append prpUseTrans
   
         End Function
   						

Steps to Reproduce Behavior

1. Open the sample database Northwind.mdb.
2. Open the Customers table and view the first record. Note that it contains the following data:
   

         CustomerID:    CompanyName:
         -----------    --------------------
         ALFKI          Alfred's Futterkiste
   						

3. Close the table. Then, create a new update query based on the Customers table, and add the following fields:
   

         Query: qryUpdateCustomers
         -------------------------
         Type: Update Query
   
         Field: CustomerID
            Criteria: "ALFKI"
         Field: CompanyName
            Update To: "Alfred's Co."
   						

4. Click anywhere in the upper portion of the QBE grid. Then, on the View menu, click Properties to view the query's property box.
5. Set the UseTransaction property to No.
6. On the Query menu, click Run. Note that you receive the message:
   

         You are about to update 1 row(s).
   
         Once you click Yes, you can't use the Undo command to reverse the
         changes. Are you sure you want to update these records?
   						

7. Click No, indicating that you do not want to commit the changes.
8. Close the query and save it as qryUpdateCustomers.
9. Open the Customers table, and view the first record. Note that now the data in the CompanyName field contains "Alfred's Co."