Creating Tables MS ACCESS with FIREDAC - delphi

Question

I am getting an error when creating tables in MS ACCESS when using FireDAC connection (Delphi Xe6).
The A new database file is created and 3 tables are created either using TFDCommand or TFDQuery, the tables do get created, but I always get an error 'Table already exists'. Any suggestions to stop the error being raised.
I do encompass the code in a try...Except routine.
Code:
FDCommand1.CommandText.Text := 'CREATE Table [SampleData] ' +
'([SampleID] INTEGER Primary Key NOT NULL, ' +
' [RiskIDX] INTEGER NULL,' +
' [RefSampleID] Char(10) NULL,' +
' [SerialNumber] Char(60) NULL,' +
' [TestDate] DateTime NULL,' +
' [ResampleDate] DateTime NULL,' +
' [SampleDate] DateTime NULL,' +
' [SamplingPoint] Char(60) NULL,' +
' [LabTech] Char(60) NULL, SampledBy Char(60) NULL,' +
' [Status] Char(60) NULL,' +
' [Source] Char(60) NULL,' +
' [Condition] Char(60) NULL,' +
' [PlotPnt] YESNO,' +
' [Comments] Memo' +
' CONSTRAINT FKSampleId Foreign Key SerialNumber
References AssetInfo SerialNo);';
OR
FDQuery1.SQL.Text := Memo1.text; //Create table SQL command
FDQuery1.Prepare;
FDQuery1.Execute(200,0);
With some experimentation I have found that the FDCommand and FDQuery components do not work in this instance; not even if you check before hand that the tables don't exist. (I not too sure why - but it seems to me that the SQL command is sent twice hence the table exists error). However, the FDConnection.ExecSQL does work. Tried and tested (creates 3 tables with the CONSTRAINTS as I needed it to).
Regards
TomD

Answer 1

I didn't test this code, but it should works in your porpouse.
function tableExists(TableName:String;Connection:TFDConnection):Boolean;
var
str: TStringList;
begin
str := TStringList.Create;
try
Connection.GetTableNames('','','',str);
result := str.IndexOf(TableName) <> -1;
finally
str.Free;
end;
end;
usage:
procedure TForm2.Button1Click(Sender: TObject);
begin
if not tableExists('SampleData',FDConnection1) then
begin
//create table here
end;
end;

Answer 2

You are calling Execute with ATimes parameter set to 200. That means that you want execute the command in array DML mode and you have 200 rows of parameter values. And since you have no parameters, it simply executes the command that number of times which fails on second attempt when DBMS rejects to create already created table.
You can either call Execute this way (there's no need for explicit call of Prepare):
FDQuery1.SQL.Text := Memo1.Text; // Create table SQL command
FDQuery1.Execute;
Or ExecSQL which internally calls Execute the way shown above:
FDQuery1.SQL.Text := Memo1.Text; // Create table SQL command
FDQuery1.ExecSQL;