1. select

1.1 将结果中的某些列与 re2 正则表达式匹配，可以使用 COLUMNS 表

1. COLUMNS(‘regexp’)

    例如表:
    CREATE TABLE default.col_names (aa Int8, ab Int8, bc Int8) ENGINE = TinyLog
    以下查询所有列名包含 a 。
    SELECT COLUMNS('a') FROM col_names
    ┌─aa─┬─ab─┐
    │  1 │  1 │
    └────┴────┘
   

2. 可以使用多个 COLUMNS 表达式并将函数应用于它们。

   例如：
   SELECT COLUMNS('a'), COLUMNS('c'), toTypeName(COLUMNS('c')) FROM col_names
    ┌─aa─┬─ab─┬─bc─┬─toTypeName(bc)─┐
    │  1 │  1 │  1 │ Int8           │
    └────┴────┴────┴────────────────┘
   

1.2 ARRAY JOIN - 数组数据平铺

样例数据：
┌─s───────────┬─arr─────┐
│ Hello       │ [1,2]   │
│ World       │ [3,4,5] │
│ Goodbye     │ []      │
└─────────────┴─────────┘

sql : 
SELECT s, arr
FROM arrays_test
ARRAY JOIN arr;
结果：
┌─s─────┬─arr─┐
│ Hello │   1 │
│ Hello │   2 │
│ World │   3 │
│ World │   4 │
│ World │   5 │
└───────┴─────┘

1.3 LEFT ARRAY JOIN

2. create

# 分布式 ddl  -  on cluster mycluster  [mycluster  是 集群名称]

2.1 分布式创建数据库

create database sztest on cluster mycluster;

2.2 分布式创建复制表

CREATE TABLE log_test ON CLUSTER mycluster
	(
	    `ts` DateTime,
	    `uid` String,
	    `biz` String
	)
	ENGINE = ReplicatedMergeTree('/clickhouse/tables/{shard}/log_test', '{replica}')
	PARTITION BY toYYYYMMDD(ts)
	ORDER BY ts
	SETTINGS index_granularity = 8192;

2.4 CREATE TABLE [IF NOT EXISTS] [db.]table_name ENGINE = engine AS SELECT …

create table file_progress_record_bak ENGINE = MergeTree(par_date,create_time,8192) as select * from daa.file_progress_record;

2.3 分布式创建分布表

create table log_test_all on CLUSTER mycluster as sztest.log_test  ENGINE =  Distributed(mycluster, sztest, log_test, rand());

备注：Distributed(mycluster, sztest, log_test, rand())，集群名，数据库名，表名，分片键[可选]

3. delete

3.1 DELETE 操作

ALTER TABLE city DELETE WHERE city=‘guangzhou’;

4. update

ALTER TABLE city UPDATE area=‘South’ WHERE city=‘wuhan’;

常用sql 汇总

1. 查询数据库表大小

WITH sum(bytes) as s
SELECT
    formatReadableSize(s),
    table
FROM system.parts
GROUP BY table
HAVING table LIKE 'http%'
ORDER BY s DESC;
或者
SELECT
    formatReadableSize(s),
    sum(bytes) as s,
    table
FROM system.parts
GROUP BY table
HAVING table LIKE 'http%'
ORDER BY s DESC;

构建日期-分钟维度表sql

CREATE TABLE datawarehouse..dim_time_minutes
(
    dt_time DateTime64(3) COMMENT '时间',
    dt_date Date COMMENT '日期'
)
ENGINE = MergeTree
PARTITION BY toYYYYMM(dt_date)
ORDER BY dt_time
SETTINGS index_granularity = 8192



truncate table datawarehouse..dim_time_minutes;
insert into datawarehouse..dim_time_minutes
select date_trunc('minute',toDateTime(num)) as dt_time,toDate(num) as dt_date from (
    select arrayJoin(
        range(
            toUInt32(toDateTime	('2028-01-01 00:00:00')),
            toUInt32(addMinutes(toDateTime('2028-12-31 23:59:00'), 1))
            )
        ) as num
    from numbers(1)
) t
group by date_trunc('minute',toDateTime(num)) as dt_time,toDate(num)
;