Excel VBA QueryTable Parameter Fails with Null Value - mysql

Question

Is it possible to pass a NULL value to QueryTable.Parameters for use in a (My)SQL query?
From this other answer, we can see that it's possible to do this with ADODB.Command, but unfortunately, ADODB is not available in Excel for Mac, and the application I'm developing should work on both Windows & Mac.
The below is confirmed to error with Windows (and I'd assume Mac).
The following VBA code works fine if you set param_value to anything but Null, but as soon as you try with a Null, it fails terribly.
Option Explicit
Sub Test()
' SQL '
Dim sql As String
sql = "SELECT ? AS `something`"
Dim param_value As Variant
'param_value = "hello" ' this works
'param_value = Null ' this does NOT work
' QUERY & TABLE CONFIG '
Dim my_dsn As String
Dim sheet_name As String
Dim sheet_range As Range
Dim table_name As String
my_dsn = "ODBC;DSN=my_dsn;"
sheet_name = "Sheet1"
Set sheet_range = Range("$A$1")
table_name = "test_table"
' EXECUTE QUERY '
Dim qt As QueryTable
Set qt = ActiveWorkbook.Worksheets(sheet_name).ListObjects.Add( _
SourceType:=xlSrcExternal, _
Source:=my_dsn, _
Destination:=sheet_range _
).QueryTable
With qt
.ListObject.Name = table_name
.ListObject.DisplayName = table_name
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.BackgroundQuery = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.PreserveColumnInfo = False
.CommandText = sql
End With
Dim param As Parameter
Set param = qt.Parameters.Add( _
"param for something", _
xlParamTypeUnknown _
)
param.SetParam xlConstant, param_value
qt.Refresh BackgroundQuery:=False
End Sub
When setting param_value to "hello", the successful result looks like this:
(This bottom part with command prompt screenshot is what was recorded by MySQL's logging).
This is the error when setting param_value to Null:
You can see from the MySQL log that the successful query first does a Prepare, followed by an Execute of the query.
Whereas the failing, Null query does the Prepare, but never makes it to the Execute.
Searching online for run-time error -2147417848 (80010108) is no help; people report getting that for everything from "freeze pane" issues to "userform" issues, and I don't see anything about this related to QueryTable.
Not only does the VBA code fail to work as expected, it also corrupts the workbook in some way:
(This occurs when attempting to save the file after the failed query; close without saving and you can re-open).
The fact that the MySQL log is showing the VBA connection failing to Quit, and that the Excel file gets corrupted, makes me think that not only is it not possible to use Null in QueryTable.Parameters, but that it is also a bug in the underlying software.
Am I missing something, or is it impossible to pass a Null Parameter to a QueryTable?
Update
In response to close votes: my point is that there should be a way to pass a parameter as NULL, just as is referenced here.
Update
Due to this issue with Null, as well as xlParamTypeDate not being converted from a decimal to 'yyyy-mm-dd', I ended up rolling my own parameterizing class module. It has been posted below as an answer to this question.

Answer 1

If anyone knows how to accomplish this with QueryTable.Parameters, then post and I'll select your answer. But following is a custom solution.
For all SqlTypes except char, the parameterization is custom, but char still uses QueryTable.Parameters due to the various escaping corner cases that can occur when trying to implement that.
Edit to above strikethrough: I have actually reverted to also manually handling char params with this custom parameterization. I forget the exact corner case encountered, but the definitive conclusion reached was that the VBA parameterization was failing for a singular case of a specific char param with a specific query string... I have absolutely no idea where the point of failure was as it was generated within the black-box of Microsoft's VBA method, but I validated as a factual certainty that the string param was simply not getting passed to the (My)SQL engine for this one seemingly random case. Suffice it to say that my experience has been that the QueryTable.Parameters method can simply not be trusted at all. My recommendation is to uncomment the line of GetValueAsSqlString = Replace$(Replace$(Replace$(CStr(value), "\", "\\"), "'", "\'"), """", "\""") and to remove the IF char THEN logic within SetQueryTableSqlAndParams. Since different engines have different literal characters, I leave this as an exercise for the reader to handle in their circumstance; for example, the above Replace$() code may (or may not) have the behavior you desire to see with a VBA string containing \n.
One inconsistency I noticed with QueryTable is that if you execute a non-parameterized query of SELECT "hello\r\nthere" AS s, the query will return with a newline (as expected), but if you use QueryTable.Parameters xlParamTypeChar with "hello\r\nthere", then it will return with raw backslashes. So you must use vbCrLf, etc. when parameterizing string literals.
SqlParams class module:
Option Explicit
' https://web.archive.org/web/20180304004843/http://analystcave.com:80/vba-enum-using-enumerations-in-vba/#Enumerating_a_VBA_Enum '
Public Enum SqlTypes
[_First]
bool
char
num_integer
num_fractional
dt_date
dt_time
dt_datetime
[_Last]
End Enum
Private substitute_string As String
Private Const priv_sql_type_index As Integer = 0
Private Const priv_sql_val_index As Integer = 1
Private params As New collection
Private Sub Class_Initialize()
substitute_string = "?"
End Sub
Public Property Get SubstituteString() As String
' This is the string to place in the query '
' i.e. "SELECT * FROM users WHERE id = ?" '
SubstituteString = substitute_string
End Property
Public Property Let SubstituteString(ByVal s As String)
substitute_string = s
End Property
Public Sub SetQueryTableSqlAndParams( _
ByVal qt As QueryTable, _
ByVal sql As String _
)
Dim str_split As Variant
str_split = Split(sql, substitute_string)
Call Assert( _
(GetArrayLength(str_split) - 1) = params.Count, _
"Found " & (GetArrayLength(str_split) - 1) & ", but expected to find " & params.Count & " of '" & substitute_string & "' in '" & sql & "'" _
)
qt.Parameters.Delete
sql = str_split(0)
Dim param_n As Integer
For param_n = 1 To params.Count
If (GetSqlType(param_n) = SqlTypes.char) And Not IsNull(GetValue(param_n)) Then
sql = sql & "?"
With qt.Parameters.Add( _
param_n, _
xlParamTypeChar _
)
.SetParam xlConstant, GetValue(param_n)
End With
Else
sql = sql & GetValueAsSqlString(param_n)
End If
sql = sql & str_split(param_n)
Next param_n
qt.CommandText = sql
End Sub
Public Property Get Count() As Integer
Count = params.Count
End Property
Public Sub Add( _
ByVal sql_type As SqlTypes, _
ByVal value As Variant _
)
Dim val_array(1)
val_array(priv_sql_type_index) = sql_type
Call SetThisToThat(val_array(priv_sql_val_index), value)
params.Add val_array
End Sub
Public Function GetSqlType(ByVal index_n As Integer) As SqlTypes
GetSqlType = params.Item(index_n)(priv_sql_type_index)
End Function
Public Function GetValue(ByVal index_n As Integer) As Variant
Call SetThisToThat( _
GetValue, _
params.Item(index_n)(priv_sql_val_index) _
)
End Function
Public Sub Update( _
ByVal index_n As Integer, _
ByVal sql_type As SqlTypes, _
ByVal value As Variant _
)
Call SetSqlType(index_n, sql_type)
Call SetValue(index_n, value)
End Sub
Public Sub SetSqlType( _
ByVal index_n As Integer, _
ByVal sql_type As SqlTypes _
)
params.Item(index_n)(priv_sql_type_index) = sql_type
End Sub
Public Sub SetValue( _
ByVal index_n As Integer, _
ByVal value As Variant _
)
Call SetThisToThat( _
params.Item(index_n)(priv_sql_val_index), _
value _
)
End Sub
Public Function GetValueAsSqlString(index_n As Integer) As String
Dim value As Variant
Call SetThisToThat(value, GetValue(index_n))
If IsNull(value) Then
GetValueAsSqlString = "NULL"
Else
Dim sql_type As SqlTypes
sql_type = GetSqlType(index_n)
Select Case sql_type
Case SqlTypes.num_integer
GetValueAsSqlString = CStr(value)
Call Assert( _
StringIsInteger(GetValueAsSqlString), _
"Expected integer, but found " & GetValueAsSqlString, _
"GetValueAsSqlString" _
)
Case SqlTypes.num_fractional
GetValueAsSqlString = CStr(value)
Call Assert( _
StringIsFractional(GetValueAsSqlString), _
"Expected fractional, but found " & GetValueAsSqlString, _
"GetValueAsSqlString" _
)
Case SqlTypes.bool
If (value = True) Or (value = 1) Then
GetValueAsSqlString = "1"
ElseIf (value = False) Or (value = 0) Then
GetValueAsSqlString = "0"
Else
err.Raise 5, "GetValueAsSqlString", _
"Expected bool of True/False or 1/0, but found " & value
End If
Case Else
' Everything below will be wrapped in quotes as a string for SQL '
Select Case sql_type
Case SqlTypes.char
err.Raise 5, "GetValueAsSqlString", _
"Use 'QueryTable.Parameters.Add' for chars"
' GetValueAsSqlString = Replace$(Replace$(Replace$(CStr(value), "\", "\\"), "'", "\'"), """", "\""") ''
Case SqlTypes.dt_date
If VarType(value) = vbString Then
GetValueAsSqlString = value
Else
GetValueAsSqlString = Format(value, "yyyy-MM-dd")
End If
Call Assert( _
StringIsSqlDate(GetValueAsSqlString), _
"Expected date as yyyy-mm-dd , but found " & GetValueAsSqlString, _
"GetValueAsSqlString" _
)
Case SqlTypes.dt_datetime
If VarType(value) = vbString Then
GetValueAsSqlString = value
Else
GetValueAsSqlString = Format(value, "yyyy-MM-dd hh:mm:ss")
End If
Call Assert( _
StringIsSqlDatetime(GetValueAsSqlString), _
"Expected datetime as yyyy-mm-dd hh:mm:ss, but found " & GetValueAsSqlString, _
"GetValueAsSqlString" _
)
Case SqlTypes.dt_time
If VarType(value) = vbString Then
GetValueAsSqlString = value
Else
GetValueAsSqlString = Format(value, "hh:mm:ss")
End If
Call Assert( _
StringIsSqlTime(GetValueAsSqlString), _
"Expected time as hh:mm:ss, but found " & GetValueAsSqlString, _
"GetValueAsSqlString" _
)
Case Else
err.Raise 5, "GetValueAsSqlString", _
"SqlType of " & GetSqlType(index_n) & " has not been configured for escaping"
End Select
GetValueAsSqlString = "'" & GetValueAsSqlString & "'"
End Select
End If
End Function
Dependency Module:
Function GetArrayLength(ByVal a As Variant) As Integer
' https://stackoverflow.com/a/30574874 '
GetArrayLength = UBound(a) - LBound(a) + 1
End Function
Sub Assert( _
ByVal b As Boolean, _
ByVal msg As String, _
Optional ByVal src As String = "Assert" _
)
If Not b Then
err.Raise 5, src, msg
End If
End Sub
Sub SetThisToThat(ByRef this As Variant, ByVal that As Variant)
' Used if "that" can be an object or a primitive '
If IsObject(that) Then
Set this = that
Else
this = that
End If
End Sub
Function StringIsDigits(ByVal s As String) As Boolean
StringIsDigits = Len(s) And (s Like String(Len(s), "#"))
End Function
Function StringIsInteger(ByVal s As String) As Boolean
If Left$(s, 1) = "-" Then
StringIsInteger = StringIsDigits(Mid$(s, 2))
Else
StringIsInteger = StringIsDigits(s)
End If
End Function
Function StringIsFractional( _
ByVal s As String, _
Optional ByVal require_decimal As Boolean = False _
) As Boolean
' require_decimal means that the string must contain a "." decimal point '
Dim n As Integer
n = InStr(s, ".")
If n Then
StringIsFractional = StringIsInteger(Left$(s, n - 1)) And StringIsDigits(Mid$(s, n + 1))
ElseIf require_decimal Then
StringIsFractional = False
Else
StringIsFractional = StringIsInteger(s)
End If
End Function
Function StringIsDate(ByVal s As String) As Boolean
StringIsDate = True
On Error GoTo no
IsObject (DateValue(s))
Exit Function
no:
StringIsDate = False
End Function
Function StringIsSqlDate(ByVal s As String) As Boolean
StringIsSqlDate = StringIsDate(s) And ( _
(s Like "####-##-##") _
Or (s Like "####-#-##") _
Or (s Like "####-##-#") _
Or (s Like "####-#-#") _
)
End Function
Function StringIsTime(ByVal s As String) As Boolean
StringIsTime = True
On Error GoTo no
IsObject (TimeValue(s))
Exit Function
no:
StringIsTime = False
End Function
Function StringIsSqlTime(ByVal s As String) As Boolean
StringIsSqlTime = StringIsTime(s) And ( _
(s Like "##:##:##") _
Or (s Like "#:##:##") _
)
End Function
Function StringIsDatetime(ByVal s As String) As Boolean
Dim n As Integer
n = InStr(s, " ")
If n Then
StringIsDatetime = StringIsDate(Left$(s, n - 1)) And StringIsTime(Mid$(s, n + 1))
Else
StringIsDatetime = False
End If
End Function
Function StringIsSqlDatetime(ByVal s As String) As Boolean
Dim n As Integer
n = InStr(s, " ")
If n Then
StringIsSqlDatetime = StringIsSqlDate(Left$(s, n - 1)) And StringIsSqlTime(Mid$(s, n + 1))
Else
StringIsSqlDatetime = False
End If
End Function
Example Usage:
Dim params As SqlParams
Set params = New SqlParams
params.Add SqlTypes.num_integer, 123
Dim sql As String
sql = "SELECT * FROM users WHERE id = " & params.SubstituteString
Dim odbc_str As String
odbc_str = "ODBC;DSN=my_dsn;"
Dim sheet As Worksheet
Set sheet = ThisWorkbook.Worksheets("Sheet1")
Dim table_name As String
table_name = "test_table"
Dim qt As QueryTable
Set qt = sheet.ListObjects.Add( _
SourceType:=xlSrcExternal, _
Source:=odbc_str, _
Destination:=Range("$A$1") _
).QueryTable
With qt
.ListObject.name = table_name
.ListObject.DisplayName = table_name
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.BackgroundQuery = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.PreserveColumnInfo = False
End With
Call params.SetQueryTableSqlAndParams(qt, sql)
qt.Refresh BackgroundQuery:=False