Caml Query tricks, Properties list, how to use caml, must read for professionals

CAML query to get all items across all folders

<QueryOptions>
        <ViewAttributes Scope="RecursiveAll" />
  </QueryOptions>

Or

query.ViewAttributes = "Scope=\"Recursive\"";

UserID for  current user (here example for Author and Editor)

<Where>
    <Or>
      <Eq>
        <FieldRef Name="Author" />
        <Value Type="Integer">
          <UserID />
        </Value>
      </Eq>
      <Eq>
        <FieldRef Name="Editor" />
        <Value Type="Integer">
          <UserID />
        </Value>
      </Eq>
    </Or>
  </Where>

UTC, Date Time format, 

ISO Caml date time format,

yyyy-MM-ddThh=mm-sss

Today
Offset "-10"

<Where>
      <Eq>
         <FieldRef Name="DueDate" />
         <Value Type="DateTime">
            <Today />
         </Value>
      </Eq>
   </Where>

OR

<Today OffsetDays='-45' />


Date Overlaps

The following example queries for cases where a recurring event overlaps with the current date and time.

<Where>
      <DateRangesOverlap>
         <FieldRef Name="EventDate" />
         <FieldRef Name="EndDate" />
         <FieldRef Name="RecurrenceID" />
         <Value Type="DateTime">
            <Now />
         </Value>
      </DateRangesOverlap>
   </Where>

Lookup ID, Lookup value

<Query>
  <Where>
    <Eq>
      <FieldRef Name="State" LookupId="TRUE" />
      <Value Type="Lookup">68</Value>
    </Eq>
  </Where>
</Query>

Multiple OR condition

<Query>
<Where>
<And>
<Geq><FieldRef Name='TaskDate' /><Value Type='DateTime'>2014-09-24T00:00:00Z</Value></Geq>
<In><FieldRef Name='Author'  />
<Values>
<Value Type='Integer'>650</Value>
<Value Type='Integer'>108</Value>
<Value Type='Integer'>1534</Value>
</Values>
</In>
</And>
</Where> 
</Query>


View Fields Fetch only mandatory columns

<QueryOptions>
        <IncludeMandotoryFields="true" />
  </QueryOptions>

many more to come...