SQLExecute('select count(*) from cars where date=''' + cars.DateTimePicker1.sqlDate + '''') <> 0 And (+cars.ComboBox1.SelectedCount+ ) > 0

1.- this query is compared with 0. Ok.

SQLExecute('select count(*) from cars where date=''' + cars.DateTimePicker1.sqlDate + '''') <> 0

2. Do you think this is the correct spelling of the ComboBox function?
- what is this?

(+cars.ComboBox1.SelectedCount+ ) > 0

   Maybe just

cars.ComboBox1.SelectedCount > 0

3. An IF with several conditions should look like this:

 IF (x>y) and (a <> b) THEN ....

4.- are you sure that in your cars table in the date column the time consists of 0?

where date='

SQLExecute('select count(*) from cars where date=''' + cars.DateTimePicker1.sqlDate + '''') <> 0 And (+cars.ComboBox1.SelectedCount+ ) > 0   then

the error in the last condition , and as i see that selected count is integer !!! why this happen