Query string options

OData supports various kinds of query options for querying data. System query options are query string parameters that control the amount and order of the data returned for the resource identified by the URL. The names of all system query options are prefixed with a dollar character, ($). A query string starts with a question mark (?), and the query options are separated by an ampersand (&). The asterisk (*) is used to specify all values. Each query option can be set on a particular value with (=).

A query string option (QueryOptions – Figure 2) can be represented in this way:

The query options admitted by the Data Hub service are listed in the following Table and described below:

Table 4 – Query Options

Query option $top

A data service URI with a $top System Query Option identifies a subset of the Entities in an EntitySet identified by the Resource Path section of the URI.

This subset is formed by selecting only the first M items of the set, where M is an integer greater than or equal to zero specified by this query option. If a value less than zero is specified, the URI should be considered malformed.

Syntax:

ONDA example:

Query option $skip

A data service URI with a $skip System Query Option identifies a subset of the Entities in an EntitySet identified by the Resource Path section of the URI.

That subset is defined by seeking N Entities into the EntitySet and selecting only the remaining Entities (starting with Entity N+1). N is an integer greater than or equal to zero specified by this query option. If a value less than zero is specified, the URI should be considered malformed.

The syntax is:

A client can request a particular page of items by combining $top and $skip.

Query option $count

The $count system query option allows clients to request a count of the matching resources included with the resources in the response.

Syntax:

ONDA example:

Query option $select

The $select system query option allows the clients to requests a limited set of properties for each entity. The value of a $select System Query Option is a comma-separated list of selection clauses.

Syntax:

ONDA example:

Query option $format

The $format system query option allows clients to request a response in a particular format. The default format is XML. Valid values for the $format query string option are:

• atom,
• xml,
• json

ONDA example:

Query option $orderby

The $orderby system query option allows clients to request resources in either ascending or descending order.

Syntax:

ONDA example:

Query option $search

A URI with a $search System Query Option identifies a subset of the Entities from an EntitySet identified by the Resource Path section of the URI. The subset is determined by selecting only the Entities that satisfy the predicate expression specified by the query option.

Syntax:

Depending on the keyword, the value(s) can be specified as a single value or range of values.

Search keywords can be combined with each other using Operators.

ONDA example: