CAML

As Small syntax error or order of tag in spquery can result any web part (or any thing in which spquery is used) doesn’t work, I’m explaining SPQuery with example, hope which may help you.

CAML (Collaborative Application Markup Language)
SPQuery is the SharePoint object which is used to perform a query operation against SharePoint data.SPList.getItems(SPQuery) is the step, will return SPListItemCollection which satisfies the query.SPQuery has one data member ‘Query’, which need to set before passing SPQuery object to SPList.

Some Properties

Properties	Description
RowLimit	Gets or sets a limit for the number of items returned in the query per page. <RowLimit>10</RowLimit> --- Can be used as: query.rowLimit = 10;
ViewFields	Gets or sets the fields that are displayed in the query. <ViewFields>         <FieldRef Name='Title'/>         <FieldRef Name='Name'/> </ViewFields> --- Can be used as:  SPQuery query = new SPQuery();  query.ViewFields = "<FieldRef Name='Field1'/>" +                       "<FieldRef Name='Field2'/>";

How to Implement SPQuery?

using (SPWeb web = SPContext.Current.Site.RootWeb)

{

    SPList mylist = web.Lists["Tasks"];

    SPQuery query = new SPQuery();

    query.Query = "<Where><Eq><FieldRef Name='Status'/>" +

                   "<Value Type='Text'>Completed</Value></Eq></Where>";

    SPListItemCollection items = mylist.GetItems(query);

    foreach (SPListItem item in items)

    {

        Response.Write(SPEncode.HtmlEncode(item["Title"].ToString()) + "<BR>");

    }

}

Operators:

Comparison Operators, Logical Joins and Order/ Group Operators, plays an important role to make this syntax.

Comparison Operators

Comparison Operators	General Meaning
Eq	=
Gt	>
Lt	<
Geq	>=
Leq	<=
Neq	<>
Contains	Like
IsNull	Null
IsNotNull	NotNull
BeginsWith	Beginning with word
DateRangesOverlap	compare the dates in a recurring event with a specified DateTime value, to determine whether they overlap

Now, to use Or between Geq and Leq conditions, we put it inside <Or> tag.

I.e. condition: where (Field1 >= 1500) or (field2 <= 500) can be written like this:

   <Where>

  <Or>

     <Geq>

         <FieldRef Name='Field1'/>

         <Value Type='Number'>1500</Value>

     </Geq>

     <Leq>

        <FieldRef Name='Field2'/><Value Type='Number'>500</Value>

     </Leq>

   </Or>

  </Where>

The full Code snippets will look like:

<View>

 <Query>

      <OrderBy>

          <FieldRef Name='ID'/>

      </OrderBy>

  <Where>

  <Or>

     <Geq>

         <FieldRef Name='Field1'/>

         <Value Type='Number'>1500</Value>

     </Geq>

     <Leq>

        <FieldRef Name='Field2'/><Value Type='Number'>500</Value>

     </Leq>

   </Or>

  </Where>

 </Query>

   <ViewFields>

        <FieldRef Name='Title'/>

        <FieldRef Name='Name'/>

   </ViewFields>

   <RowLimit>10</RowLimit>

</View>

Example: Contains, And, BeginsWith

The following example uses the Contains element that is assigned to the Query property to return the titles of items where the Conference column value begins with "Morning" and contains "discussion session".

<Where>

   <And>

       <BeginsWith>

              <FieldRef Name="Conference"/>

              <Value Type="Note">Morning</Value>

       </BeginsWith>

       <Contains>

              <FieldRef Name="Conference" />

              <Value Type="Note">discussion session</Value>

       </Contains>

   </And>

</Where>

Example: DateRangesOverlap

<Where>

     <DateRangesOverlap>

          <FieldRef Name="EventDate"></FieldRef>

          <FieldRef Name="EndDate"></FieldRef>

          <FieldRef Name="RecurrenceID"></FieldRef>

            <Value Type="DateTime">

              <Now/>

            </Value>

     </DateRangesOverlap>

</Where>

Logical Joins:

Logical Joins	Comments
And	Used within the ‘Where’ element to  group filters in a query for a view
Or	Used within the ‘Where’ element  to group filters in a query for a view

Example: And

<Where>

   <And>

     <Neq>

        <FieldRef Name="Status"></FieldRef>

        <Value Type="Text">Completed</Value>

     </Neq>

     <IsNull>

        <FieldRef Name="Sent"></FieldRef>

     </IsNull>

   </And>

</Where>

Order/Group Operators:

Order/Group Operators	Comments
OrderBy	Determines the sort order for a query. The OrderBy element contains a group of FieldRef elements I.e.  <OrderBy> <FieldRef Name="Title" Ascending="TRUE"> </FieldRef> </OrderBy>
GroupBy	Contains a Group By section for grouping the data returned through a query in a list view

Example: OrderBy

<OrderBy>

       <FieldRef Name="Modified" Ascending="FALSE"></FieldRef>

</OrderBy>

<Where>

  <Or>

    <Neq>

      <FieldRef Name="Status"></FieldRef>

      <Value Type="Text">Completed</Value>

    </Neq>

    <IsNull>

      <FieldRef Name="Status"></FieldRef>

    </IsNull>

  </Or>

</Where>

Example: GroupBy

<GroupBy>

      <FieldRef Name="Modified"/>

</GroupBy>

<Where>

   <Or>

      <Neq>

          <FieldRef Name="Status"></FieldRef>

          <Value Type="Text">Completed</Value>

      </Neq>

      <IsNull>

          <FieldRef Name="Status"></FieldRef>

      </IsNull>

   </Or>

</Where>

Important:

This is very important thing to keep in mind, because SPQuery will be assigned as a string so it wont show compile time error though it may have tag syntax error, not in order, escape sequence error, etc.

Escape sequence:

The ScriptEncode method escapes characters that would otherwise conflict with script.

Original	Replacement
"	\"
\	\\
+	\u002b
>	\u003e
<	\u003c
'	\u0027

Example:

<FieldRef Name=\"Checkbox\"></FieldRef> <Value Type=\"bit\">1</Value>

Thanks