Sharepoint CAML Fliter - sharepoint-2010

Question

I have a SharePoint page which shows new employees from an employee list. I uses the start date of the employee and displays them for 30 days. We have outsourced 2 departments and managers do not want to see them as new employees since they are from a third party firm. Below is the code I tried but can not get to work. I have moved the 'And' up to include all three filter and I get an error '(soap:ServerException of t.SharePoint.SoapServer.SoapServerException' was thrown. Cannot complete this action. Please try again.0x80004005)'.
I move the 'And' near the 'Neq' and they get ignored. I am trying to keep the 30 days for start date and exclude the two departments.
`<Query>
<OrderBy>
<FieldRef Name="Full_x0020_Name"/>
</OrderBy>
<Where>
<And>
<Geq>
<FieldRef Name="StartDate"/>
<Value Type="DateTime">
<Today OffsetDays="-30"/>
</Value>
</Geq>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">G4S Security</Value>
</Neq>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">Budd Group</Value>
</Neq>
</And>
</Where>
</Query>`

Answer 1

I found a solution, there can be only two within an And. This is the code I changed below.
'<Where>
<And>
<And>
<Geq>
<FieldRef Name="StartDate"/>
<Value Type="DateTime">
<Today OffsetDays="-30"/>
</Value>
</Geq>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">G4S Security</Value>
</Neq>
</And>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">Budd Group</Value>
</Neq>
</And>
</Where>'

Answer 2

https://msdn.microsoft.com/en-us/library/office/ms196939(v=office.14).aspx
This element can be nested inside other And and Or elements. The server supports unlimited complicated queries. However, any given And element can have only two conjuncts; that is, only two child elements. If you need to conjoin three or more conditions, you must nest the And elements [...]
<Where>
<And>
<And>
<Geq>
<FieldRef Name="StartDate"/>
<Value Type="DateTime">
<Today OffsetDays="-30"/>
</Value>
</Geq>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">G4S Security</Value>
</Neq>
</And>
<Neq>
<FieldRef Name="Department"/>
<Value Type="Text">Budd Group</Value>
</Neq>
</And>
</Where>

Answer 3

There is also the issue of the query method itself.
If you are using the method "query" in the "list" class, then you cannot use the <Query></Query> tags in your CAML. The reason is the method already wraps your query with this tag automatically and adding it breaks the query.
See my code for example:
Private Function GenerateCamlForCurrentUserMessages(list As SPList, isActiveOnly As Boolean) As SPQuery
Dim qResult As SPQuery
Dim sCaml As String = ""
Dim web As SPWeb = SPContext.Current.Web
If isActiveOnly Then
sCaml = "<Where><And><Eq><FieldRef Name='Author' /><Value Type='User'>" & web.CurrentUser.Name.ToString() & "</Value></Eq><Eq><FieldRef Name='IsActive' /><Value Type='Boolean'>1</Value></Eq></And></Where>"
Else
sCaml = "<Where><Eq><FieldRef Name='Author' /><Value Type='User'>" & web.CurrentUser.Name.ToString() & "</Value></Eq></Where>"
End If
qResult = New SPQuery()
'sCaml = sCaml & list.DefaultView.Query
qResult.Query = sCaml
Return qResult
End Function