CAML Query error when more than 2 variables in OR - sharepoint

Question

In my SharePoint CAML query, when filtering with two input, it is successful. However, when I have 3 or more, it failed.
Is there a different format to be used when using more than two inputs?
Pass (2 fields):
<Where>
<And>
<Or>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H1</Value></Eq>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H2</Value></Eq>
</Or>
<Neq><FieldRef Name ="ContentType"/><Value Type="Text">Document</Value></Neq>
</And>
</Where>
Fail (3 fields):
<Where>
<And>
<Or>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H1</Value></Eq>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H2</Value></Eq>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H3</Value></Eq>
</Or>
<Neq><FieldRef Name ="ContentType"/><Value Type="Text">Document</Value></Neq>
</And>
</Where>
Error:
Cannot complete this action. Please try again. at
Microsoft.SharePoint.SPGlobal.HandleComException(COMException comEx)
at
Microsoft.SharePoint.Library.SPRequest.GetListItemDataWithCallback2(IListItemSqlClient
pSqlClient, String bstrUrl, String bstrListName, String bstrViewName,
String bstrViewXml, SAFEARRAYFLAGS fSafeArrayFlags,
ISP2DSafeArrayWriter pSACallback, ISPDataCallback pPagingCallback,
ISPDataCallback pPagingPrevCallback, ISPDataCallback
pFilterLinkCallback, ISPDataCallback pSchemaCallback, ISPDataCallback
pRowCountCallback, Boolean& pbMaximalView) at
Microsoft.SharePoint.SPListItemCollection.EnsureListItemsData() at
Microsoft.SharePoint.SPListItemCollection.get_Count()

Answer 1

In the CAML syntax, both <Or> and <And> and binary operators. Hence they must have two operands only. If you need more, you have to nest them accordingly. In your case:
<Where>
<And>
<Or>
<Or>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H1</Value></Eq>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H2</Value></Eq>
</Or>
<Eq><FieldRef Name="Header1Ref"/><Value Type="Text">H3</Value></Eq>
</Or>
<Neq><FieldRef Name ="ContentType"/><Value Type="Text">Document</Value></Neq>
</And>
</Where>