Browsing a Queue Table | CREATE TABLE | Teradata Vantage - Browsing a Queue Table - Analytics Database - Teradata Vantage

SQL Data Definition Language Detailed Topics

Deployment
VantageCloud
VantageCore
Edition
Enterprise
IntelliFlex
VMware
Product
Analytics Database
Teradata Vantage
Release Number
17.20
Published
June 2022
Language
English (United States)
Last Update
2023-07-11
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B035-1184
lifecycle
latest
Product Category
Teradata Vantage™

To browse a queue table is to select from it as you would a non-queue table.

The following list of queries provides some peeks at a queue without consuming any rows.
  • You can determine the queue depth of a queue table by using the COUNT(*) aggregate function, as follows.
    SELECT COUNT(*)
    FROM myqueue;

    If the depth is zero, then the system places a consume mode SELECT statement into a delayed state.

  • You can peek at the next row set that would be consumed from the queue table using the following query.
    SELECT *
    FROM shoppingcart
    WHERE qits = (SELECT MIN(qits)
                  FROM shoppingcart);
  • The following query selects only the next ten rows to be consumed.
    SELECT TOP 10 *
    FROM myqueue
    ORDER BY QITS;
  • The following query, a browse mode SELECT statement, returns the entire queue in FIFO order.
    SELECT *
    FROM myqueue
    ORDER BY myqueue_qits;
  • The duration of a queue table measures how old the top queue table row is.

    To determine the duration of a queue table, you can execute the following statement:

    SELECT TOP 1 CURRENT_TIMESTAMP, qits, (CURRENT_TIMESTAMP - qits)       DAY(4) TO SECOND AS queue_duration
    FROM shoppingcart
    ORDER BY qits;

    This query generates a report similar to the following:

        *** Query completed. One row found. 3 columns returned.
    Current Timestamp (6)  2004-05-19 14:30:01.420000+00:00
    Q Insertion Time   2004-05-18 08:44:19.460000
    queue_duration      1 05:45:41.960000