ADODB CreateParameter in SELECT without specifying Parameter in CommandText - sql-server

Question

Using SQL Server Express 2014 with Access 2016
Front end contains a form intended to be used to search for records in the database. The VBA code on the submit for the form builds the WHERE of the SELECT statement as one long string.
This is an abbreviated example.
Set thisDb = DBEngine.Workspaces(0).Databases(0)
Set qDef = thisDb.CreateQueryDef("tempPTQ")
qDef.Connect = "ODBC;Driver={ODBC Driver 11 for SQL Server};SERVER=" & stServer & ";DATABASE=" & stDatabase & ";Trusted_Connection=Yes;"
strFields = "field1, field2, field3"
strTable = "dbo_SomeTable"
strParam = "WHERE field1=" & txtBox1.Value & ", AND field2=" & txtBox2.Value & ", AND field3=" & txtBox3.Value
strSQL = "SELECT " & strFields & " FROM " & strTable & " WHERE " & strParam & ";"
qDef.SQL = strSQL
DoCmd.RunSQL "INSERT INTO " & strDestTbl & " SELECT * FROM tempPTQ"
Is it possible to convert this to an ADODB parameterized query with a dynamic WHERE clause, essentially a variable number of columns, each represented by a different parameter?
strSQL = "SELECT field1, field2, field3 FROM someTable"
Set dbCon = New ADODB.Connection
With dbCon
.ConnectionString = "Driver={SQL Server Native Client 11.0};SERVER=" & stServer & ";DATABASE=" & stDatabase & ";Trusted_Connection=Yes;"
.Open
End With
Set dbCmd = New ADODB.Command
With dbCmd
.ActiveConnection = dbCon
.CommandText = strSQL
If txtBox1.Value <> "" Then
.CreateParameter("param1", adChar)
.Parameters(0).Value = txtBox1.Value
End If
If txtBox2.Value <> "" Then
.CreateParameter("param2", adChar)
.Parameters(1).Value = txtBox2.Value
End If
If txtBox3.Value <> "" Then
.CreateParameter("param3", adChar)
.Parameters(2).Value = txtBox3.Value
End If
Set rst = .Execute()
rst.Close
Set rst = Nothing
End With
How can parameters be dynamically added to the WHERE clause?

Answer 1

Consider using a collection that holds the WHERE clause statement with ? placeholders and a dictionary of corresponding parameters:
Private Function FilterCriteria() As Collection
Dim sqlCollection As New Collection
Dim strCriteria As String
Dim params As Object
Set params = CreateObject("Scripting.Dictionary")
strCriteria = "1 = 1" ' ALWAYS TRUE CONDITION TO START WHERE CLAUSE
If txtBox1.Value <> "" Then
strCriteria = strCriteria & " AND field1 = ?"
params.Add "field1param", txtBox1.Value
End If
If txtBox2.Value <> "" Then
strCriteria = strCriteria & " AND field2 = ?"
params.Add "field2param", txtBox2.Value
End If
If txtBox3.Value <> "" Then
strCriteria = strCriteria & " AND field3 = ? "
params.Add "field3param", txtBox3.Value
End If
sqlCollection.Add strCriteria
sqlCollection.Add params
Set FilterCriteria = sqlCollection
End Function
Then in your actual database call, retrieve above function's returned collection and use in prepared statement and .CreateParameters:
Dim sqlCollection As New Collection
Set sqlCollection = FilterCriteria ' CALLING ABOVE FUNCTION (RETURNED COLLECTION)
Set dbCon = New ADODB.Connection
With dbCon
.ConnectionString = "Driver={SQL Server Native Client 11.0};SERVER=" & _
stServer & ";DATABASE=" & stDatabase & ";Trusted_Connection=Yes;"
.Open
End With
' CONCATENATE WHERE CLAUSE STRING TO SQL STATEMENT
strSQL = "SELECT field1, field2, field3 FROM someTable WHERE " & sqlCollection(1)
Set dbCmd = New ADODB.Command
With dbCmd
.ActiveConnection = dbCon
.CommandText = strSQL
' BIND PARAMETERS FROM PARAMS DICT (KEYS=NAME, VALUES=PARAM VALUE)
For Each key In sqlCollection(2).keys
cmd.Parameters.Append cmd.CreateParameter(key, adVarChar, adParamInput, 255, _
sqlCollection(2)(key))
Next key
Set rst = .Execute()
rst.Close
Set rst = Nothing
End With