Question

我想在选定的模式中选择所需的结果，如此

column_name  |  data_type   | description
-----------------------------------------
id           | integer      |  id of bill
name         | character    |
address      | character    | adress of buyer

请注意，有些列没有说明（列注释）。

现在我只得到了这个查询，它给了我很好的结果，但只针对得到注释的列（对于所选表中没有注释的列没有在输出中表示）。

我的查询只返回下一个有评论的列的数据

SELECT c.column_name, c.data_type, pgd.description 
from pg_catalog.pg_statio_all_tables as st 
inner join pg_catalog.pg_description pgd on (pgd.objoid=st.relid) 
inner join information_schema.columns c on (pgd.objsubid=c.ordinal_position and  c.table_schema=st.schemaname and c.table_name=st.relname)  
where table_schema = 'public' and table_name = 'some_table';

如何在结果中获取没有评论的列？

Answer 1

有功能col_description(table_oid, column_number)

select column_name, data_type, col_description('public.my_table'::regclass, ordinal_position)
from information_schema.columns
where table_schema = 'public' and table_name = 'my_table';

 column_name | data_type |  col_description  
-------------+-----------+-------------------
 gid         | integer   | a comment for gid
 id          | integer   | 
 max_height  | numeric   | 
(3 rows)

Answer 2

因为information_schema.columns是包含数据的表格，并且您不是第一个引用它，所以您需要right outer join代替：

t=# SELECT c.column_name, c.data_type, pgd.description
from pg_catalog.pg_statio_all_tables as st
inner join pg_catalog.pg_description pgd on (pgd.objoid=st.relid)
right outer join information_schema.columns c on (pgd.objsubid=c.ordinal_position and  c.table_schema=st.schemaname and c.table_name=st.relname)
where table_schema = 'public' and table_name = 's150';
  column_name  | data_type | description
---------------+-----------+-------------
 customer_name | text      |
 order_id      | text      |
 order_date    | date      |
(3 rows)

Answer 3

在 col_description() 上使用 pg_attribute：

select
  attname as column_name,
  atttypid::regtype as data_type,
  col_description(attrelid, attnum) as description
from pg_attribute
where attrelid = '(myschema.)mytable'::regclass
  and attnum > 0        -- hide system columns
  and not attisdropped  -- hide dead/dropped columns
order by attnum;

PostgreSQL，获取列名，列类型和描述

3 个答案: