VBA Wait for DoCmd.RunSQL OR Better Query - Ms Access - sql

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:
A way to tell VBA to "wait for previous command" OR
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.

Answer 2

Try something like this (Note I've commented your DoCmd.RunSQL. I changed it with db.Execute:
Sub DeleteInsertData(tables() As String, toDB As String, fromDB As String)
Dim db As DAO.Database
Dim i As Integer
Dim SQL As String
Set db = CurrentDb()
For i = 0 To UBound(tables)
'Delete all data first
SQL = "DELETE * FROM " & tables(i)
db.Execute SQL, dbFailOnError
'DoCmd.RunSQL SQL
'Update all data second
SQL = "INSERT INTO " & tables(i) & " IN """ & toDB & """ SELECT " & tables(i) & " .* FROM " & tables(i) & " IN """ & fromDB & """;"
db.Execute SQL, dbFailOnError
'DoCmd.RunSQL SQL
Next
Set db = Nothing
End Sub

Answer 3

I'm no expert, but I don't think you need the DELETE part. SELECT INTO is the syntax for making a table. If the table already exists, it's overwritten.

Answer 4

If I need to wait for something, I tend to use DoEvents to allow windows to process any other actions that have been put on hold.
From the help: "Yields execution so that the operating system can process other events."
Found this:
.BeginTrans then
.CommitTrans dbForceOSFlush
as a way to force updates to be written before continuing