>>Yes, very simple...
>>
>>

>>SELECT Client.Numero
>> FROM Client
>> LEFT JOIN Invoice ON Invoice.Numero=Client.NoInvoice AND Invoice.SecondCondition=True
>> LEFT JOIN Inventory ON Inventory.Numero=Client.NoInventory AND Inventory.SecondCondition=True
>>WHERE Invoice.Numero IS NOT NULL OR Inventory.Numero IS NOT NULL
>>

>
>This does not work.

What do you mean by it's not working? You don't get correct results? It should be the same as your other query with EXISTS.