我创建了一个小工具来查询和比较数据库模式: Dump PostgreSQL数据库模式到文本

有关于FK的信息，但ollyc的回复提供了更多的细节。

以下是Andreas Joseph Krogh从PostgreSQL邮件列表提供的解决方案:http://www.postgresql.org/message-id/200811072134.44750.andreak@officenet.no

SELECT source_table::regclass, source_attr.attname AS source_column,
    target_table::regclass, target_attr.attname AS target_column
FROM pg_attribute target_attr, pg_attribute source_attr,
  (SELECT source_table, target_table, source_constraints[i] source_constraints, target_constraints[i] AS target_constraints
   FROM
     (SELECT conrelid as source_table, confrelid AS target_table, conkey AS source_constraints, confkey AS target_constraints,
       generate_series(1, array_upper(conkey, 1)) AS i
      FROM pg_constraint
      WHERE contype = 'f'
     ) query1
  ) query2
WHERE target_attr.attnum = target_constraints AND target_attr.attrelid = target_table AND
      source_attr.attnum = source_constraints AND source_attr.attrelid = source_table;

这个解决方案处理引用多个列的外键，并避免重复(其他一些答案无法做到这一点)。我唯一改变的是变量名。

下面是一个示例，返回所有引用权限表的雇员列:

SELECT source_column
FROM foreign_keys
WHERE source_table = 'employee'::regclass AND target_table = 'permission'::regclass;

$1 ('my_schema')是模式，$2 ('my_table')是表名:

SELECT ss.conname constraint_name, a.attname column_name, ss.refnamespace fk_table_schema, ss.reflname fk_table_name, af.attname fk_column_name
    FROM  pg_attribute a, pg_attribute af,
        (SELECT r.oid roid, c.conname, rf.relname reflname, information_schema._pg_expandarray(c.conkey) x,
                nrf.nspname refnamespace, rf.oid rfoid, information_schema._pg_expandarray(cf.confkey) xf
            FROM pg_namespace nr, pg_class r, pg_constraint c,
                pg_namespace nrf, pg_class rf, pg_constraint cf
            WHERE nr.oid = r.relnamespace
                AND r.oid = c.conrelid
                AND rf.oid = cf.confrelid
                AND c.conname = cf.conname
                AND nrf.oid = rf.relnamespace
                AND nr.nspname = $1
                AND r.relname = $2) ss
    WHERE ss.roid = a.attrelid AND a.attnum = (ss.x).x AND NOT a.attisdropped
        AND ss.rfoid = af.attrelid AND af.attnum = (ss.xf).x AND NOT af.attisdropped
    ORDER BY ss.conname, a.attname;

为了扩展Martin的精彩回答，这里有一个查询，它允许您根据父表进行过滤，并显示每个父表的子表的名称，以便您可以根据父表中的外键约束查看所有依赖的表/列。

select 
    con.constraint_name,
    att2.attname as "child_column", 
    cl.relname as "parent_table", 
    att.attname as "parent_column",
    con.child_table,
    con.child_schema
from
   (select 
        unnest(con1.conkey) as "parent", 
        unnest(con1.confkey) as "child", 
        con1.conname as constraint_name,
        con1.confrelid, 
        con1.conrelid,
        cl.relname as child_table,
        ns.nspname as child_schema
    from 
        pg_class cl
        join pg_namespace ns on cl.relnamespace = ns.oid
        join pg_constraint con1 on con1.conrelid = cl.oid
    where  con1.contype = 'f'
   ) con
   join pg_attribute att on
       att.attrelid = con.confrelid and att.attnum = con.child
   join pg_class cl on
       cl.oid = con.confrelid
   join pg_attribute att2 on
       att2.attrelid = con.conrelid and att2.attnum = con.parent
   where cl.relname like '%parent_table%'       

现有的答案都没有给出我想要的结果。这是我的(庞大的)查询，用于查找有关外键的信息。

注意事项:

The expressions used to generate from_cols and to_cols could be vastly simplified on Postgres 9.4 and later using WITH ORDINALITY rather than the window-function-using hackery I'm using. Those same expressions are relying on the query planner not altering the returned order of results from UNNEST. I don't think it will, but I don't have any multiple-column foreign keys in my dataset to test with. Adding the 9.4 niceties eliminates this possibility altogether. The query itself requires Postgres 9.0 or later (8.x didn't allow ORDER BY in aggregate functions) Replace STRING_AGG with ARRAY_AGG if you want an array of columns rather than a comma-separated string.

-

SELECT
    c.conname AS constraint_name,
    (SELECT n.nspname FROM pg_namespace AS n WHERE n.oid=c.connamespace) AS constraint_schema,

    tf.name AS from_table,
    (
        SELECT STRING_AGG(QUOTE_IDENT(a.attname), ', ' ORDER BY t.seq)
        FROM
            (
                SELECT
                    ROW_NUMBER() OVER (ROWS UNBOUNDED PRECEDING) AS seq,
                    attnum
                FROM
                    UNNEST(c.conkey) AS t(attnum)
            ) AS t
            INNER JOIN pg_attribute AS a ON a.attrelid=c.conrelid AND a.attnum=t.attnum
    ) AS from_cols,

    tt.name AS to_table,
    (
        SELECT STRING_AGG(QUOTE_IDENT(a.attname), ', ' ORDER BY t.seq)
        FROM
            (
                SELECT
                    ROW_NUMBER() OVER (ROWS UNBOUNDED PRECEDING) AS seq,
                    attnum
                FROM
                    UNNEST(c.confkey) AS t(attnum)
            ) AS t
            INNER JOIN pg_attribute AS a ON a.attrelid=c.confrelid AND a.attnum=t.attnum
    ) AS to_cols,

    CASE confupdtype WHEN 'r' THEN 'restrict' WHEN 'c' THEN 'cascade' WHEN 'n' THEN 'set null' WHEN 'd' THEN 'set default' WHEN 'a' THEN 'no action' ELSE NULL END AS on_update,
    CASE confdeltype WHEN 'r' THEN 'restrict' WHEN 'c' THEN 'cascade' WHEN 'n' THEN 'set null' WHEN 'd' THEN 'set default' WHEN 'a' THEN 'no action' ELSE NULL END AS on_delete,
    CASE confmatchtype::text WHEN 'f' THEN 'full' WHEN 'p' THEN 'partial' WHEN 'u' THEN 'simple' WHEN 's' THEN 'simple' ELSE NULL END AS match_type,  -- In earlier postgres docs, simple was 'u'nspecified, but current versions use 's'imple.  text cast is required.

    pg_catalog.pg_get_constraintdef(c.oid, true) as condef
FROM
    pg_catalog.pg_constraint AS c
    INNER JOIN (
        SELECT pg_class.oid, QUOTE_IDENT(pg_namespace.nspname) || '.' || QUOTE_IDENT(pg_class.relname) AS name
        FROM pg_class INNER JOIN pg_namespace ON pg_class.relnamespace=pg_namespace.oid
    ) AS tf ON tf.oid=c.conrelid
    INNER JOIN (
        SELECT pg_class.oid, QUOTE_IDENT(pg_namespace.nspname) || '.' || QUOTE_IDENT(pg_class.relname) AS name
        FROM pg_class INNER JOIN pg_namespace ON pg_class.relnamespace=pg_namespace.oid
    ) AS tt ON tt.oid=c.confrelid
WHERE c.contype = 'f' ORDER BY 1;

 SELECT 
    conrelid::regclass AS table_from,
    conname,
    pg_get_constraintdef(oid) as condef    
    FROM pg_catalog.pg_constraint r

也适用于所有约束条件。例如，使用pysql: