>>Well, to me the re-factored command is much easier to understand and debug. But it's up to you to take the suggestion and try it or not.
>
>This would be better:
>
>

>...
>     WHERE BusinessTime.NoProvince=
>      (SELECT COALESCE((SELECT Company.NoProvince FROM Company WHERE Company.NoCountry=1 AND Company.Numero=Client.NoCompany),84)) AND
>      BusinessTime.NoHoliday=0 AND
>      BusinessTime.Start<Client.FirstDate AND
>      BusinessTime.[End]>=Client.SecondDate) Temp)
>...
>

This would not work. You're not getting NULL, you're not getting result at all.