CTAS 示例

以下示例为 EVENT 表创建名为 EVENT_BACKUP 的表：

create table event_backup as select * from event;

生成的表继承 EVENT 表中的分配键和排序键。

select "column", type, encoding, distkey, sortkey
from pg_table_def where tablename = 'event_backup';

column    | type                        | encoding | distkey | sortkey
----------+-----------------------------+----------+---------+--------
catid     | smallint                    | none     | false   |       0
dateid    | smallint                    | none     | false   |       1
eventid   | integer                     | none     | true    |       0
eventname | character varying(200)      | none     | false   |       0
starttime | timestamp without time zone | none     | false   |       0
venueid   | smallint                    | none     | false   |       0

以下命令通过选择 EVENT 表中的四个列来创建一个名为 EVENTDISTSORT 的新表。新表按 EVENTID 进行分配并按 EVENTID 和 DATEID 进行排序：

create table eventdistsort
distkey (1)
sortkey (1,3)
as
select eventid, venueid, dateid, eventname
from event;

结果如下：

select "column", type, encoding, distkey, sortkey
from pg_table_def where tablename = 'eventdistsort';

column   |          type          | encoding | distkey | sortkey
---------+------------------------+----------+---------+-------
eventid   | integer               | none     | t       | 1
venueid   | smallint              | none     | f       | 0
dateid    | smallint              | none     | f       | 2
eventname | character varying(200)| none     | f       | 0      

可通过对分配键和排序键使用列名来创建完全相同的表。例如：

create table eventdistsort1
distkey (eventid)
sortkey (eventid, dateid)
as
select eventid, venueid, dateid, eventname
from event;

以下语句对表应用 EVEN 分配，但不定义明确的排序键。

create table eventdisteven
diststyle even
as
select eventid, venueid, dateid, eventname
from event;

该表不继承 EVENT 表 (EVENTID) 中的排序键，因为已为新表指定 EVEN 分配。新表没有排序键和分配键。

select "column", type, encoding, distkey, sortkey
from pg_table_def where tablename = 'eventdisteven';

column    |          type          | encoding | distkey | sortkey
----------+------------------------+----------+---------+---------
eventid   | integer                | none     | f       | 0
venueid   | smallint               | none     | f       | 0
dateid    | smallint               | none     | f       | 0
eventname | character varying(200) | none     | f       | 0       

以下语句应用 EVEN 分配并定义排序键：

create table eventdistevensort diststyle even sortkey (venueid)
as select eventid, venueid, dateid, eventname from event;

生成的表具有排序键，但不具有分配键。

select "column", type, encoding, distkey, sortkey
from pg_table_def where tablename = 'eventdistevensort';

column    |          type          | encoding | distkey | sortkey
----------+------------------------+----------+---------+-------
eventid   | integer                | none     | f       | 0
venueid   | smallint               | none     | f       | 1
dateid    | smallint               | none     | f       | 0
eventname | character varying(200) | none     | f       | 0      

以下语句基于来自传入数据（基于 EVENTID 列进行排序）的其他键列重新分配 EVENT 表，但不定义 SORTKEY 列；因此，不会对表进行排序。

create table venuedistevent distkey(venueid)
as select * from event;

结果如下：

select "column", type, encoding, distkey, sortkey
from pg_table_def where tablename = 'venuedistevent';

 column   |            type             | encoding | distkey | sortkey
----------+-----------------------------+----------+---------+-------
eventid   | integer                     | none     | f       | 0
venueid   | smallint                    | none     | t       | 0
catid     | smallint                    | none     | f       | 0
dateid    | smallint                    | none     | f       | 0
eventname | character varying(200)      | none     | f       | 0
starttime | timestamp without time zone | none     | f       | 0