如何从 pg_constraint 获取列名

Question

我需要从数据库中获取约束列表并将它们与它们相关的列进行匹配对于此任务，我将使用 pg_constraint。这是我使用的查询

 select conrelid::regclass AS table_from, conname, pg_get_constraintdef(c.oid)
from   pg_constraint c
join   pg_namespace n ON n.oid = c.connamespace
 where conrelid::regclass::text = 'test' order by contype;

如您所见，我对名为 test 的 table 的约束感兴趣这是输出

table_from |    conname     | pg_get_constraintdef 
------------+----------------+----------------------
 test       | test_age_check | CHECK ((age > 0))

但我想使用上面的查询获取此约束的列名（在本例中，列是 age）。根据docColumn constraints are not treated specially。但也许有一些方法可以用来从 pg_constraint 中检索列名？

Answer 1

pg_constrint.conkey 包含 table 中列序数的数组。您可以使用它们加入 pg_attribute。这里的序号在 attnum.

列中

SELECT c.conrelid::regclass AS table_from,
       c.conname,
       pg_get_constraintdef(c.oid),
       a.attname
       FROM pg_constraint c
            INNER JOIN pg_namespace n
                       ON n.oid = c.connamespace
            CROSS JOIN LATERAL unnest(c.conkey) ak(k)
            INNER JOIN pg_attribute a
                       ON a.attrelid = c.conrelid
                          AND a.attnum = ak.k
       WHERE c.conrelid::regclass::text = 'test'
       ORDER BY c.contype;

如何从 pg_constraint 获取列名

How to get column name from pg_constraint

postgresql

psql