Browsing a Queue Table | VantageCloud Lake - Browsing a Queue Table

To browse a queue table, select from it.

The following queries peek at a queue without consuming rows.

Determine the queue depth of a queue table by using the COUNT(*) aggregate function:
```
SELECT COUNT(*)
FROM myqueue;
```
If the depth is zero, the system puts a consume mode SELECT statement into a delayed state.

Peek at the next row set to be consumed from the queue table:

SELECT *
FROM shoppingcart
WHERE qits = (SELECT MIN(qits)
              FROM shoppingcart);

Select only the next ten rows to be consumed:
```
SELECT TOP 10 *
FROM myqueue
ORDER BY QITS;
```

Return the entire queue in FIFO order:

SELECT *
FROM myqueue
ORDER BY myqueue_qits;

The duration of a queue table measures the age of the top queue table row.

Determine the duration of a queue table:

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

The result is similar to this:

    *** 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

Browsing a Queue Table | VantageCloud Lake - Browsing a Queue Table - Teradata VantageCloud Lake

Lake - Working with SQL