PostgreSQL "DESCRIBE TABLE“

Question

如何在PostgreSQL中执行等同于Oracle的DESCRIBE TABLE (使用psql命令)？

Answer 1

尝试以下命令(在psql命令行工具中)：

\d+ tablename

有关详细信息，请参阅the manual。

Answer 2

除了序列方式(\d 'something‘或\dt’PostgreSQL‘或\ds 'sequence’等)

SQL标准方式，如here所示

select column_name, data_type, character_maximum_length, column_default, is_nullable
from INFORMATION_SCHEMA.COLUMNS where table_name = '<name of table>';

它被许多数据库引擎所支持。

Answer 3

如果您想要从query而不是psql获取它，您可以查询目录模式。下面是一个复杂的查询，可以做到这一点：

SELECT  
    f.attnum AS number,  
    f.attname AS name,  
    f.attnum,  
    f.attnotnull AS notnull,  
    pg_catalog.format_type(f.atttypid,f.atttypmod) AS type,  
    CASE  
        WHEN p.contype = 'p' THEN 't'  
        ELSE 'f'  
    END AS primarykey,  
    CASE  
        WHEN p.contype = 'u' THEN 't'  
        ELSE 'f'
    END AS uniquekey,
    CASE
        WHEN p.contype = 'f' THEN g.relname
    END AS foreignkey,
    CASE
        WHEN p.contype = 'f' THEN p.confkey
    END AS foreignkey_fieldnum,
    CASE
        WHEN p.contype = 'f' THEN g.relname
    END AS foreignkey,
    CASE
        WHEN p.contype = 'f' THEN p.conkey
    END AS foreignkey_connnum,
    CASE
        WHEN f.atthasdef = 't' THEN d.adsrc
    END AS default
FROM pg_attribute f  
    JOIN pg_class c ON c.oid = f.attrelid  
    JOIN pg_type t ON t.oid = f.atttypid  
    LEFT JOIN pg_attrdef d ON d.adrelid = c.oid AND d.adnum = f.attnum  
    LEFT JOIN pg_namespace n ON n.oid = c.relnamespace  
    LEFT JOIN pg_constraint p ON p.conrelid = c.oid AND f.attnum = ANY (p.conkey)  
    LEFT JOIN pg_class AS g ON p.confrelid = g.oid  
WHERE c.relkind = 'r'::char  
    AND n.nspname = '%s'  -- Replace with Schema name  
    AND c.relname = '%s'  -- Replace with table name  
    AND f.attnum > 0 ORDER BY number
;

它相当复杂，但它确实向您展示了PostgreSQL系统目录的功能和灵活性，并且应该可以帮助您掌握pg_catalog ;-)。请确保更改查询中的%s。第一个是Schema，第二个是表名。