interface
 
uses
  System.SysUtils,
  System.StrUtils,
  System.Variants;
 
function VarToSql(const pValue: Variant; pTrimToNull: Boolean = True; 
  pDateTimeFormat: string = 'dd.mm.yyyy hh:nn:ss:zzz'; 
  pQuoteDate: Boolean = True; pQuoteDateChar: Char = ''''; 
  pNullString: string = 'NULL'): string;
 
 
implementation
 
function VarToSql(const pValue: Variant; pTrimToNull: Boolean; 
  pDateTimeFormat: string; pQuoteDate: Boolean; pQuoteDateChar: Char; 
  pNullString: string): string;
var
  FDecimalSeparatorOld: Char;
  FValue              : Variant;
begin
  FValue := pValue;
  if pNullString.Trim.IsEmpty then
    pNullString := 'NULL';
  case AnsiIndexText(VarTypeAsText(VarType(FValue)), ['FMTBcdVariantType']) of
    0:
      FValue := VarAsType(FValue, varDouble);
    // poderão ser adicionados mais tipos específicos
  end;
 
// varSingle, varDouble, varCurrency
  if VarIsFloat(FValue) then
    with FormatSettings do
    begin
      FDecimalSeparatorOld := DecimalSeparator;
      DecimalSeparator := '.';
      Result := FloatToStr(FValue, FormatSettings);
      DecimalSeparator := FDecimalSeparatorOld;
    end;
 
{varSmallInt, varInteger, varBoolean, varShortInt, varByte, varWord, 
   varLongWord, varInt64, varUInt64}
  if VarIsOrdinal(FValue) then
    Result := VarToStr(FValue);
 
// varOleStr, varString, varUString
  if VarIsStr(FValue) then
    Result := QuotedStr(FValue);
 
// varDate
  if VarIsType(FValue, varDate) then
    Result := IfThen(pQuoteDate, AnsiQuotedStr(FormatDateTime(pDateTimeFormat, 
              VarToDateTime(FValue)), pQuoteDateChar),
              FormatDateTime(pDateTimeFormat, VarToDateTime(FValue)));
 
  if ((VarIsClear(FValue)) or (VarIsNull(FValue)) or 
      (VarIsEmpty(FValue)) or (VarIsError(FValue))) then
    Result := pNullString;
 
  if pTrimToNull then
    if (Result.Trim.IsEmpty) or (Result.DeQuotedString.Trim.IsEmpty) then
      Result := pNullString;
end;

Sql := VarToSql(DateEdit.Date);
Sql := VarToSql(DataSet.FieldByName('valor').AsCurrency);
Sql := VarToSql(FNome);