DWS与Greenplum一些语法差异总结

一．建表语法

1. DWS建表语法-分区表

create table green
(
        id int,
        school varchar(50),
        sale int,
        place  varchar(50),
        begintime timestamp
)with(orientation = column,compression = low)
distribute by hash(id)
partition by range(begintime)
(
        partition p1 values less than('2019-06-05 00:00:00'),
        partition p2 values less than('2019-06-06 00:00:00')
);

 普通表：

create table blue
(
        id int,
        school varchar(50),
        endtime timestamp
)with(orientation=column,compression=low)
distribute by hash(id);

2. Greenplum建表语法-分区表

create table green
(
        id int,
        school varchar(50),
        sale int,
        place  varchar(50),
        begintime timestamp
)with(appendonly = true, orientation = column)
distributed by (id)
partition by range(begintime)
(
        partition p1 start('2019-06-05 00:00:00') inclusive end('2019-06-06 00:00:00') exclusive,
        partition p2 start('2019-06-06 00:00:00') inclusive end('2019-06-07 00:00:00') exclusive,
        default partition default_p
);

普通表：

create table blue
(
        id int,
        school varchar(50),
        endtime timestamp
)with(appendonly = true, orientation = column)
distributed by (id);

3. 建表语法差异点：

二．创建视图：(DWS和Greenplum的视图创建无差异)

create view person as
select a.sex as sexa,b.sex as sexb from test_person a left join test_person1 b on a.id = b.id;

查询视图

select * from person;

三．创建函数:(下面这个函数两者无差异)

DWS：

create or replace function increment_plsql(i integer) returns integer
as $$
begin
        return i+1;
end
$$ LANGUAGE plpgsql;

Greenplum:

create or replace function increment_plsql(i integer) returns integer
as $$
begin
        return i+1;
end
$$ LANGUAGE plpgsql;

四．Greenplum导出文件

1.greenplum中可使用pg_dump备份数据库中的元数据

pg_dump -U {user_name} -W {password} -p {port} {database_name} -s -C -f dump.sql

2. greenplum中使用pg_dump备份数据库中的数据

pg_dump -U {user_name} -W {password} -p {port} {database_name} -a -C -f dump_data.sql

DWS可使用gsql客户端中提供的gs_dump工具，用法与pg_dump类似。 

五．使用copy命令导入导出数据

Greenplum的copy用法：

1.csv格式导出，默认分隔符是","

copy test_person to '/home/gpadmin/jinyuze/test_person.csv' with csv;

2.csv格式导出，分隔符设置为"|"

copy test_person to '/home/gpadmin/jinyuze/test_person1.csv' with csv delimiter as '|';

使用copy命令从文件中导入数据到一张表中

1.copy jinyuze from '/home/gpadmin/jinyuze/result/test_person1.csv' with delimiter as '|';
2.copy jinyuze from '/home/gpadmin/jinyuze/result/test_person.csv' with csv;

注：公有云DWS默认是安全模式，是禁止直接使用copy命令进行导入导出数据的，如果想要使用copy，需要在命令前面添加 "\",例如：

\copy jinyuze from '/home/gpadmin/jinyuze/result/test_person.csv' with csv;