Postgresql：复合类型并选择进入

Posted 2023-05-08

【中文标题】Postgresql：复合类型并选择进入

【英文标题】：Postresql: Composite types and select into

【发布时间】：2016-09-01 10:26:26

【问题描述】：

有人可以解释一下吗？ （一切都在下面的例子中！）。我使用postgresql 9.4。 警告！在下面的代码中，我删除了“object type”复合类型和“example_data”临时表，请确保您的数据库中没有这些...以防万一，我注释了 drop 命令，如果需要，请取消注释它们。 ..

--drop type if exists object_type;
--drop table if exists example_data;

create type object_type as (
       id text
       ,value text);

create temporary table example_data as (
       select
            'id1'::text as id,
            'example value'::text as value);

do $$
declare
    my_object object_type;
begin

    -- The fiolowing doesn't work, we can't use INTO with the whole object
    -- Some how, it tries to put the whole object into the first attribute:
    select (id,value)::object_type
    into my_object
    from example_data;

    raise warning 'ID: %, VALUE: %', my_object.id, my_object.value;

    -- What a shame! It would have been so much more convenient than the following:    
    -- to feed the object we need to repeat each one of the attribute in the INTO section:
    select id, value
    into  my_object.id, my_object.value
    from example_data;

    raise warning 'ID: %, VALUE: %', my_object.id, my_object.value;

/*
In that example it is not so bad, but when you have very large object, it is very ugly to repeat each one
of the attribute, for example:
select  (att1, att2, att3, att4, att5, att6, att7, att8, att9, att10)::object_type2 into my_object2

and, (very heavy):
select  att1, att2, att3, att4, att5, att6, att7, att8, att9, att10
into my_object2.att1, my_object2.att2, my_object2.att3, my_object2.att4, my_object2.att5, my_object2.att6,
     my_object2.att7, my_object2.att8, my_object2.att9, my_object2.att10

*/

end $$;

--drop type if exists object_type;
--drop table if exists example_data;

【参考方案1】：

关注the documentation:

...
select id, value
into my_object
from example_data;
...