我的caml查询无法正常工作

Question

以下caml查询有什么问题？

    <Where>
    <And><Or>
    <Neq><FieldRef Name='NumberOfPcsRemaining' />
    <Value  Type='Calculated'>0</Value></Neq>
    <IsNull><FieldRef Name='OutForDeliveryDateTime' /></IsNull>
    </Or>
    <And>
    <Includes><FieldRef Name='ServiceType'  /> 
    <Value Type='LookupMulti'>Delivery</Value></Includes>
    <And>
    <Neq><FieldRef Name='BBAStatus'  />
    <Value Type='Text'>BBA not Completed</Value> </Neq>
    <And> 
    <IsNotNull><FieldRef Name='IncidentReport'  /></IsNotNull>
    <Eq><FieldRef Name='OkToDeliver' /><Value Type='Boolean'>1</Value></Eq>
    </And>
    </And>
    </And> 
    </And>
    </Where>

即使它有价值，似乎下面的部分总是会成真。

  <IsNull><FieldRef Name='OutForDeliveryDateTime' /></IsNull>