使用列的默認值創建 KSQL stream？

Question

是否可以從 Kafka 主題創建 stream 主題中不存在的一些列的默認值或固定值？

create stream test
(
Balance BIGINT,
Name STRING <---- want to specify a fix value ("NA" or "no name")  for this column which is not in topic data
)
with (kafka_topic='test_topic', value_format='JSON');

Answer 1

您不能在針對該主題創建初始 stream 時執行此操作，但您可以使用coalesce創建派生的 stream ：

create stream test
    (Balance BIGINT,
     Name    STRING )
    with (kafka_topic='test_topic', value_format='JSON');

create stream test_2 AS
    SELECT BALANCE, 
           COALESCE(Name, 'No Name') as name
    from test;