ksql 使用

https://docs.ksqldb.io/en/latest/developer-guide/ksqldb-reference/

注意执行命令要在ksqldb-server 而不是 ksqldb-cli 的容器下面

stream 和 table 的区别是，table必须定义primary key，而且执行了query后下次还可以拿到数据，而stream是没有的

ksql> print bear from beginning;

 

CREATE STREAM pageviews_original (viewtime bigint, userid varchar, pageid varchar) WITH (kafka_topic='pageviews', value_format='DELIMITED');

 

CREATE TABLE users_original (registertime bigint primary key, gender varchar, regionid varchar, userid varchar) WITH (kafka_topic='users', value_format='JSON');

 

ksql> select * from USERS_ORIGINAL emit changes limit 5;

ksql> select * from users_original where rowtime >='2022-03-18' emit changes;

ksql> show queries;

stream 和 table都可以insert data

ksql> insert into stream_test values('1',1,1,1);

ksql> insert into users_original(REGISTERTIME,GENDER,REGIONID,USERID) values(1,'G1','G1','G1');

想count的话只能通过group by 的操作，数据量大的话会是个灾难

ksql> select key,count(*) from stream_test group by key emit changes;

 ksql> select count(*) from stream_test group by 1 emit changes;

可以用describe extended 命令查询

ksql> describe stream_test extended;

 

Oftentimes—and particularly in testing and development—you’ll want to read the data that already exists in a topic. To tell KSQL to do this, change the offset property:

ksql> SET 'auto.offset.reset'='earliest';

 

update table 的话可以通过join语法创建个新表来实现

KSQL statement to update values in table?