count/Count

count/Count — Static and dynamic aggregate functions for count

SYNOPSIS

Count()

count()

DESCRIPTION

Returns the number of rows that meet the query predicate conditions.

  • For static aggregation, aggregates refresh as data in the active (source) table is updated.

  • For dynamic aggregation, aggregates refresh as rows are returned by the query predicate.

The function name is case-sensitive. The Title-cased syntax is for static (table-based) aggregation. The lower-cased syntax is for dynamic (query-based) aggregation. See Data Aggregation for more information on aggregation in LiveView.

EXAMPLE

This example shows you how to issue a dynamic aggregation query against a LiveView server instance that counts the number of items that have a low inventory.

Load and run the Hello LiveView sample as delivered with LiveView. Follow these steps:

  1. Start StreamBase Studio in the SB Authoring perspective.

  2. Load the Hello LiveView sample.

    1. Select File → Load StreamBase Sample from Studio's top-level menu.

    2. In the Load StreamBase Projects dialog, open the StreamBase LiveView category.

    3. Select the sample whose description is Shows a simple Hello World application and press OK.

    The Hello LiveView sample loads into Studio with the project name sample_lv-helloliveview.

  3. In the Package Explorer view, select the name of the project, right-click, and from the context menu, select Run As → StreamBase LiveView Project. The Console view shows several messages as the LiveView Server compiles the project and starts.

  4. When you see message All tables have been loaded in the Console view, start LiveView Desktop:

    • On Windows, run Start → All Programs → StreamBase LiveView n.m → LiveView Desktop.

    • On Linux, run the following command: 

      /opt/streambase/liveview/desktop/liveview &

    This opens the LiveView Desktop start dialog.

  5. In the LiveView Desktop start dialog, select the radio button for Download and click Select.

  6. Select the workspace named Hello LiveView and version Latest (1.0).

  7. Click OK. This returns you to the LiveView Desktop start dialog. The Download field now contains Hello LiveView (Latest).

  8. Click OK.

Now you can count the number of items that have low inventory.

  1. Select the ItemsSales table from the Tables pane of the LiveView Tables view.

  2. In the Query on ItemsSales pane, enter the following:

    1. In the Select window, enter: 

      count(if (quantityRemaining < 10) then true else bool()) as lowInventory

    2. Click Open Query.

The query results open, by default, in a grid view. The count aggregate will update when the number of rows returned by the query changes.