前言

hivesql中很多常用的功能，过段时间没有使用就容易忘记，需要去网上搜索，这里总结一下，省的以后还去去搜，供自己以后参考。

查看分区的行

show rowcount extended table_name;

创建二级分区表

set hive.default.fileformat=Orc;
use db_name;
CREATE TABLE IF NOT EXISTS tb_name(col_name1 STRING comment '',col_name2 STRING comment '',col_name3 STRING comment '',col_name4 STRING comment '',col_name5 STRING comment ''
)COMMENT 'for demo'
PARTITION BY LIST(col_name) 
SUBPARTITION BY LIST (col_name2) (SUBPARTITION default) ( PARTITION default)
STORED AS ORCFILE COMPRESS;

alter表(增加列)

use db_name;
ALTER TABLE tb_name ADD COLUMNS (cols_name6 string COMMENT ''
);

alter表(drop列)

# 不写即删除， 删除col_name4，col_name5，col_name6，保留col_name1，col_name2，col_name3
use db_name;
ALTER TABLE tb_name ADD COLUMNS (col_name1 STRING comment '',col_name2 STRING comment '',col_name3 STRING comment ''
);

删除表

use db_name;
drop table tb_name;

insert分区数据

# 将p_20221231分区的数据，写到p_20230101分区，注意分区名和值的统一，否则会写入失败
use db_name;
alter table tb_name drop partition (p_20230101);
alter table tb_name add partition p_20230101 values in(20230101);
insert table tb_name partition(col_name1=20230101)
select'20230101' as col_name1,col_name2, col_name3, col_name4
from tb_name
partition ( p_20221231)p

case-when操作

 selectcol_name1,col_name2, col_name3, col_name4，case when col_name3 is null then CONCAT_WS('-', col_name1, col_name2)when col_name4 is null then CONCAT_WS('-', col_name1, col_name2, col_name3)else col_name1end as new_col_namefrom tb_name partition(p_20230101)t

LATERAL VIEW操作

col_name4的值为(字符串)：‘{ “list_value”: [value1, value2]}’

# col_name4的值为："[value1, value2]"
# 先将其col_name3转为json，然后获取list_value的值，接着使用regexp_replace替换掉("[]")等，变成字符串。再接着使用split分割成数组，并使用explode将其打平。selectcol_name1,col_name2, col_name3, col_name4，id_tmpfrom tb_name partition(p_20230101)tLATERAL VIEW explode(split(regexp_replace(get_json_object(col_name4, '$.list_value'), "\"|\"|\\[|\\]", ''), ',')) id_list as id_tmp

分组排序编号，获取topK操作

# 
SELECT *
from (SELECT col_name1,col_name2, row_number() over (partition by col_name2, col_name3 order by col_name4 desc) rank rankfrom tb_name
)
where rank < 500