Question

I have a query which uses an array of tables (stored as a string array) to loop through my tables and perform a Delete/Update set of queries. The queries are identical other than the table names, hence using a loop to iterate through using the table name as a variable.

The problem is, my Delete query locks the table and the Update query runs too quickly afterward; I get a “db is locked” error.

I need either of two things:

1. A way to tell VBA to “wait for previous command” OR
2. A way to concatenate these queries into one (or two) queries: one to delete the database rows and another to import the new ones. With this I could just run the queries from a standard access query (which should allocate proper time, finish queries etc)

The only catch to this is that there are parent-child relations, so the parent table has to be updated before its children (currently accomplished through array ordering).

Here’s the current code which (sometimes) produces the “DB locked/in use” message:

For i = 0 To UBound(tables)
    'Delete all data first
    sql = "DELETE * FROM " & tables(i)
    DoCmd.RunSQL sql
    'Update all data second
    sql = "INSERT INTO " & tables(i) & " IN """ & toDB & """ SELECT " & tables(i) & " .* FROM " & tables(i) & " IN """ & fromDB & """;"
    DoCmd.RunSQL sql
Next

Should clarify: the queries take one backend’s (fromDB) rows from identical tables and pushes it to another backend’s (toDB) rows

EDIT: In response to the questions regarding INSERT INTO, my problem with that is if I add fields to the toDB, it will delete them if I overwrite. The reason I have to do this backdoor approach is because the database is still in development, but is also being used with select tables. Updates and feature improvements are done daily. I cannot use a simple split-backend either, because the other computer accessing the database is not always on the network (we have to manually sync it when it returns to the network), so I work on one backend and it works on another, identical(ish, minus my schema update) backend.

Answer 1

You can use ADO instead of DoCmd.RunSQL to execute your SQL synchronously.

 Dim cmd As ADODB.Command
 Dim cnn As New ADODB.Connection

 Set cnn = CurrentProject.Connection

 For i = 0 To UBound(tables)
     Set cmd = New ADODB.Command
     With cmd

        .CommandType = adCmdText
         .ActiveConnection = cnn
        .CommandText = "DELETE * FROM " & tables(i)
        .Execute
      End With

     Set cmd = New ADODB.Command
     With cmd

        .CommandType = adCmdText
         .ActiveConnection = cnn
        .CommandText = "INSERT INTO " & tables(i) & " IN """ & toDB & """ SELECT " & tables(i) & " .* FROM " & tables(i) & " IN """ & fromDB & """;"
        .Execute
      End With

Next

You could also add cnn.BeginTrans and cnn.CommitTrans to make the two statements Atomic.