sql - 如何使用 PostgreSQL 从表名中获取列属性查询？

Question

我有一个项目，我需要一个查询来获取列的所有属性(列名、位置、数据类型、非空？和注释)所有这些都使用表名。

我实现了获取列名、位置数据类型和非空？使用此查询:

SELECT column_name, data_type, ordinal_position, is_nullable 
FROM information_schema."columns"
WHERE "table_name"='TABLE-NAME'

但是，我需要评论!

Answer 1

这是针对 system catalog 的查询那应该获取您需要的所有内容(免费提供一个额外的主键字段)。

SELECT DISTINCT
    a.attnum as num,
    a.attname as name,
    format_type(a.atttypid, a.atttypmod) as typ,
    a.attnotnull as notnull, 
    com.description as comment,
    coalesce(i.indisprimary,false) as primary_key,
    def.adsrc as default
FROM pg_attribute a 
JOIN pg_class pgc ON pgc.oid = a.attrelid
LEFT JOIN pg_index i ON 
    (pgc.oid = i.indrelid AND i.indkey[0] = a.attnum)
LEFT JOIN pg_description com on 
    (pgc.oid = com.objoid AND a.attnum = com.objsubid)
LEFT JOIN pg_attrdef def ON 
    (a.attrelid = def.adrelid AND a.attnum = def.adnum)
WHERE a.attnum > 0 AND pgc.oid = a.attrelid
AND pg_table_is_visible(pgc.oid)
AND NOT a.attisdropped
AND pgc.relname = 'TABLE_NAME'  -- Your table name here
ORDER BY a.attnum;

这将返回如下结果:

 num |    name     |             typ             | notnull |       comment       | primary_key 
-----+-------------+-----------------------------+---------+---------------------+-------------
   1 | id          | integer                     | t       | a primary key thing | t
   2 | ref         | text                        | f       |                     | f
   3 | created     | timestamp without time zone | t       |                     | f
   4 | modified    | timestamp without time zone | t       |                     | f
   5 | name        | text                        | t       |                     | f

• num: 列号
• name: 列名
• typ:数据类型
• notnull:列是否定义为NOT NULL
• comment:为列定义的任何COMMENT
• primary_key:是否列定义为PRIMARY KEY
• default: 用于默认值的命令