PostgreSQL“DESCRIBE TABLE”
你如何在PostgreSQL中执行相当于Oracle的DESCRIBE TABLE （使用psql命令）？
试试这个（在psql命令行工具中）：
d+ tablename
有关更多信息，请参阅手册。
除了PostgreSQL方法（ d'something'或 dt'table'或 ds'序列'等）外，
SQL标准方式，如下所示：
select column_name, data_type, character_maximum_length
from INFORMATION_SCHEMA.COLUMNS where table_name = '<name of table>';
它受到许多数据库引擎的支持。
如果你想从查询而不是psql中获得它，你可以查询目录模式。 这是一个复杂的查询：
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
;
这非常复杂，但它确实向您展示了PostgreSQL系统目录的强大功能和灵活性，并且可以帮助您完成pg_catalog mastery ;-)。 一定要改变查询中的％s。 第一个是Schema，第二个是表名。
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