clickhouse 问题汇总

Nullable字段作为排序字段

Nullable字段作为排序字段（order by） 

报错：Code: 44. DB::Exception: Sorting key contains nullable columns, but merge tree setting `allow_nullable_key` is disabled.

排序字段不可包含Nullable列， 解决方法：建表语句后加 settings allow_nullable_key=1;

参考：https://kb.altinity.com/engines/mergetree-table-engine-family/altinity-kb-nulls-in-order-by/

clickhouse 筛选数组不考虑数组内顺序

对字段排序后筛选

 select * from analysis where arrayReverseSort(analysis_comb) in(['71','330'],['80','337'])

mysql 同步到clickhouse

SET allow_experimental_database_materialized_mysql = 1;
CREATE DATABASE clickhouse_db_name ENGINE = MaterializedMySQL('host:port', 'database', 'user', 'password') -- mysql 的数据库参数
SETTINGS materialized_mysql_tables_list ='table1, table2';  -- 指定表，不指定时同步全部库中的表