数据量不小，不能全量存储， 数据缓慢变化的维度数据

拉链表的建表语句--全量表 通过有效起始时间<=时间<=有效结束时间来获取维度的全量切片数据

建表语句

drop table if exists dwd_dim_user_info_his;

create external table dwd_dim_user_info_his(

`id` string COMMENT '用户 id',

`name` string COMMENT '姓名',

`birthday` string COMMENT '生日',

`gender` string COMMENT '性别',

`email` string COMMENT '邮箱',

`user_level` string COMMENT '用户等级',

`create_time` string COMMENT '创建时间',

`operate_time` string COMMENT '操作时间',

`start_date` string COMMENT '有效开始日期',

`end_date` string COMMENT '有效结束日期'

) COMMENT '用户拉链表'

stored as parquet

location '/warehouse/gmall/dwd/dwd_dim_user_info_his/'

tblproperties ("parquet.compression"="lzo");

已有的一些数据表

drop table if exists ods_user_info;

create external table ods_user_info(

`id` string COMMENT '用户 id',

`name` string COMMENT '姓名',

`birthday` string COMMENT '生日',

`gender` string COMMENT '性别',

`email` string COMMENT '邮箱',

`user_level` string COMMENT '用户等级',

`create_time` string COMMENT '创建时间',

`operate_time` string COMMENT '操作时间'

) COMMENT '用户表'

PARTITIONED BY (`dt` string)

row format delimited fields terminated by '\t'

STORED AS

INPUTFORMAT 'com.hadoop.mapred.DeprecatedLzoTextInputFormat'

OUTPUTFORMAT 'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

location '/warehouse/gmall/ods/ods_user_info/';

数据示例:

20200101ods数据

id create_time operate_time

1 20200101 20200101

20200102 ods数据，产生修改的数据

1 20200101 20200102

20200103 ods数据，产生修改的数据

1 20200101 20200103

2 20200103 20200103

20200101拉链表

1 20200101 9999-99-99

20200102拉链表数据

1 20200101 20200101

1 20200102 9999-99-99

20200103拉链表数据

1 20200101 20200101

1 20200102 20200102

1 20200103 9999-99-99

2 20200103 9999-99-99

步骤一：初始化拉链表(以某一天为基准日期，这一天的数据都当成是新增数据)

select

id,

name,

birthday,

gender,

email,

user_level,

create_time,

operate_time,

'20200101' as start_date,

'9999-99-99' as end_date

from

ods_user_info

where

dt = '20200101'

步骤二:制作当日变动数据(新增、修改)

insert overwrite table dwd_dim_user_info_his_tmp --先导入临时表。再通过临时表导入正式表

select

user_his.id,

user_his.name,

user_his.birthday,

user_his.gender,

user_his.email,

user_his.user_level,

user_his.create_time,

user_his.operate_time,

user_his.start_date,

if(

update_user.end_date is not null

and user_his.end_date = '9999-99-99',

'20200101',

user_his.end_date

) as end_date

from

(

select

id,

name,

birthday,

gender,

email,

user_level,

create_time,

operate_time,

start_date,

end_date

from

dwd_dim_user_info_his

where

dt = '20200101'

) user_his

left join (

select

id,

name,

birthday,

gender,

email,

user_level,

from

ods_user_info

where

dt = '20200102'

) update_user on user_his.id = update_user.id

union all

select

id,

name,

birthday,

gender,

email,

user_level,

create_time,

operate_time,

'20200102' as start_date,

'9999-99-99' as end_date

from

ods_user_info

where

dt = '20200102'