Eof not triggering - sql-server

Question

I have a function where I get data from a DB, my test data set returns 6500 rows (I extracted the formatted SQL statement from the SQLText Variable and ran it as a test), but then when I run the following code Eof never triggers and I have seen over 100k rows imported.
ADOQuery := TADOQuery.Create(nil);
ADOQuery.ConnectionString := CONNECT_STRING;
// Build SQL Query
SQLText := Format( 'Select Temp.Serial, Temp.QCSample , Temp.Scrap , Temp.StationID , Temp.Defect , Temp.AddData , Temp2.Serial as Parent_Serial ' +
'from TAB_ELEMENT as Temp ' +
'left join TAB_ELEMENT as Temp2 on Temp.Parent_Id = Temp2.Element_Id ' +
'where Temp.Batch_ID = %d and Temp.StationID = 0 ',[iSearchID]);
ADOQuery.SQL.Clear; // Clear query of garbage values
ADOQuery.SQL.Text := SQLText; // Add query text to query module
ADOQuery.Open;
// Handle Results
iIndexPos := 0;
tDataImport.BeginUpdate;
while not ADOQuery.Eof do
begin
tDataImport.Items[iIndexPos].Serial := ADOQuery.FieldByName('Serial').AsString;
tDataImport.Items[iIndexPos].QCStatus := ADOQuery.FieldByName('QCSample').AsBoolean;
tDataImport.Items[iIndexPos].Scrap := ADOQuery.FieldByName('Scrap').AsInteger;
tDataImport.Items[iIndexPos].StationID := ADOQuery.FieldByName('StationID').AsInteger;
tDataImport.Items[iIndexPos].Defect := ADOQuery.FieldByName('Defect').AsBoolean;
tDataImport.Items[iIndexPos].AddData := ADOQuery.FieldByName('AddData').AsString;
tDataImport.Items[iIndexPos].ParentSerial := ADOQuery.FieldByName('Parent_Serial').AsString;
inc(iIndexPos);
end;
So in summery running this query with these parameters I expect 6500 rows, when I run this it never ends even after 100k+ rows are processed.

Answer 1

Open() places the cursor on the first record and sets Eof accordingly. You are not calling Next() to advance the cursor to the next record and update Eof, so you are processing the same record over and over:
ADOQuery.Open;
while not ADOQuery.Eof do
begin
//...
ADOQuery.Next; // <-- add this!
end;
On a side note, you should be using a parameterized query instead of a formatted SQL query string. It is safer, faster, and more efficient on the DB:
ADOQuery := TADOQuery.Create(nil);
ADOQuery.ConnectionString := CONNECT_STRING;
ADOQuery.SQL.Text := 'Select Temp.Serial, Temp.QCSample , Temp.Scrap , Temp.StationID , Temp.Defect , Temp.AddData , Temp2.Serial as Parent_Serial ' +
'from TAB_ELEMENT as Temp ' +
'left join TAB_ELEMENT as Temp2 on Temp.Parent_Id = Temp2.Element_Id ' +
'where Temp.Batch_ID = :iSearchID and Temp.StationID = 0 ';
with ADOQuery.Parameters.ParamByName('iSearchID') do
begin
DataType := ftInteger;
Value := iSearchID;
end;
ADOQuery.Open;
try
iIndexPos := 0;
tDataImport.BeginUpdate;
try
while not ADOQuery.Eof do
begin
tDataImport.Items[iIndexPos].Serial := ADOQuery.FieldByName('Serial').AsString;
tDataImport.Items[iIndexPos].QCStatus := ADOQuery.FieldByName('QCSample').AsBoolean;
tDataImport.Items[iIndexPos].Scrap := ADOQuery.FieldByName('Scrap').AsInteger;
tDataImport.Items[iIndexPos].StationID := ADOQuery.FieldByName('StationID').AsInteger;
tDataImport.Items[iIndexPos].Defect := ADOQuery.FieldByName('Defect').AsBoolean;
tDataImport.Items[iIndexPos].AddData := ADOQuery.FieldByName('AddData').AsString;
tDataImport.Items[iIndexPos].ParentSerial := ADOQuery.FieldByName('Parent_Serial').AsString;
inc(iIndexPos);
ADOQuery.Next;
finally
tDataImport.EndUpdate;
end;
end;
finally
ADOQuery.Close;
end;