如何列出表外键

你可以使用PostgreSQL系统目录。也许你可以查询pg_constraint来获取外键。 你也可以使用信息模式

您可以通过information_schema表来实现这一点。例如:

SELECT
tc.table_schema,
tc.constraint_name,
tc.table_name,
kcu.column_name,
ccu.table_schema AS foreign_table_schema,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu
ON tc.constraint_name = kcu.constraint_name
AND tc.table_schema = kcu.table_schema
JOIN information_schema.constraint_column_usage AS ccu
ON ccu.constraint_name = tc.constraint_name
AND ccu.table_schema = tc.table_schema
WHERE tc.constraint_type = 'FOREIGN KEY' AND tc.table_name='mytable';

PSQL就是这样做的，如果你用:

psql -E

它将准确地显示执行了哪些查询。在查找外键的情况下，它是:

SELECT conname,
pg_catalog.pg_get_constraintdef(r.oid, true) as condef
FROM pg_catalog.pg_constraint r
WHERE r.conrelid = '16485' AND r.contype = 'f' ORDER BY 1

在这种情况下，16485是我正在寻找的表的oid -你可以通过将你的表名转换为regclass来获得它:

WHERE r.conrelid = 'mytable'::regclass

如果表名不是唯一的(或者是search_path中的第一个)，则对表名进行模式限定:

WHERE r.conrelid = 'myschema.mytable'::regclass

有关于FK的信息，但ollyc的回复提供了更多的细节。

使用Key所引用的主键的名称并查询information_schema:

select table_name, column_name
from information_schema.key_column_usage
where constraint_name IN (select constraint_name
from information_schema.referential_constraints
where unique_constraint_name = 'TABLE_NAME_pkey')

这里'TABLE_NAME_pkey'是外键引用的主键的名称。

SELECT r.conname
,ct.table_name
,pg_catalog.pg_get_constraintdef(r.oid, true) as condef
FROM pg_catalog.pg_constraint r, information_schema.constraint_table_usage ct
WHERE r.contype = 'f'
AND r.conname = ct.constraint_name
ORDER BY 1

我写了一个解决方案，喜欢和经常使用。代码位于http://code.google.com/p/pgutils/。看这些小疙瘩。foreign_keys视图。

不幸的是，输出太冗长，这里不包括。但是，你可以在数据库的公共版本上尝试一下，就像这样:

$ psql -h unison-db.org -U PUBLIC -d unison -c 'select * from pgutils.foreign_keys;

这至少适用于8.3版本。如果需要的话，我预计会在未来几个月内对其进行更新。

莉丝

检查ff帖子的解决方案，不要忘记标记这个，当你认为这是有帮助的

http://errorbank.blogspot.com/2011/03/list-all-foreign-keys-references-for.html

SELECT
o.conname AS constraint_name,
(SELECT nspname FROM pg_namespace WHERE oid=m.relnamespace) AS source_schema,
m.relname AS source_table,
(SELECT a.attname FROM pg_attribute a WHERE a.attrelid = m.oid AND a.attnum = o.conkey[1] AND a.attisdropped = false) AS source_column,
(SELECT nspname FROM pg_namespace WHERE oid=f.relnamespace) AS target_schema,
f.relname AS target_table,
(SELECT a.attname FROM pg_attribute a WHERE a.attrelid = f.oid AND a.attnum = o.confkey[1] AND a.attisdropped = false) AS target_column
FROM
pg_constraint o LEFT JOIN pg_class f ON f.oid = o.confrelid LEFT JOIN pg_class m ON m.oid = o.conrelid
WHERE
o.contype = 'f' AND o.conrelid IN (SELECT oid FROM pg_class c WHERE c.relkind = 'r');

扩展到ollyc配方:

CREATE VIEW foreign_keys_view AS
SELECT
tc.table_name, kcu.column_name,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage
AS kcu ON tc.constraint_name = kcu.constraint_name
JOIN information_schema.constraint_column_usage
AS ccu ON ccu.constraint_name = tc.constraint_name
WHERE constraint_type = 'FOREIGN KEY';

然后:

SELECT * FROM foreign_keys_view WHERE table_name='YourTableNameHere';

Ollyc的答案很好，因为它不是特定于postgres的，但是，当外键引用多个列时，它就会崩溃。以下查询适用于任意数量的列，但它严重依赖于Postgres扩展:

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

这个查询也适用于组合键:

select c.constraint_name
, x.table_schema as schema_name
, x.table_name
, x.column_name
, y.table_schema as foreign_schema_name
, y.table_name as foreign_table_name
, y.column_name as foreign_column_name
from information_schema.referential_constraints c
join information_schema.key_column_usage x
on x.constraint_name = c.constraint_name
join information_schema.key_column_usage y
on y.ordinal_position = x.position_in_unique_constraint
and y.constraint_name = c.unique_constraint_name
order by c.constraint_name, x.ordinal_position

我认为你想要的和@ollyc写的很接近的是:

SELECT
tc.constraint_name, tc.table_name, kcu.column_name,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu
ON tc.constraint_name = kcu.constraint_name
JOIN information_schema.constraint_column_usage AS ccu
ON ccu.constraint_name = tc.constraint_name
WHERE constraint_type = 'FOREIGN KEY' AND ccu.table_name='YourTableNameHere';

这将列出所有使用指定表作为外键的表

下面是Andreas Joseph Krogh从PostgreSQL邮件列表中提供的解决方案: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。

下面是一个返回所有引用permission表的employee列的示例:

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

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%'

在PostgreSQL提示符下发出\d+ tablename，除了显示表列的数据类型外，它还会显示索引和外键。

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:

• 用于生成from_cols和to_cols的表达式可以在Postgres 9.4和以后使用WITH ORDINALITY而不是我正在使用的使用窗口函数的hack进行极大简化。
• 这些相同的表达式依赖于查询计划器不改变UNNEST返回结果的顺序。我认为不会，但我的数据集中没有任何多列外键可以测试。添加9.4细节完全消除了这种可能性。
• 查询本身需要Postgres 9.0或更高版本(8。x不允许ORDER BY在聚合函数中)
• 如果你想要一个列的数组，而不是逗号分隔的字符串，将STRING_AGG替换为ARRAY_AGG。

-

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;

注意:在读取约束列时，不要忘记列的顺序!

SELECT conname, attname
FROM pg_catalog.pg_constraint c
JOIN pg_catalog.pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY (c.conkey)
WHERE attrelid = 'schema.table_name'::regclass
ORDER BY conname, array_position(c.conkey, a.attnum)

另一种方式:

WITH foreign_keys AS (
SELECT
conname,
conrelid,
confrelid,
unnest(conkey)  AS conkey,
unnest(confkey) AS confkey
FROM pg_constraint
WHERE contype = 'f' -- AND confrelid::regclass = 'your_table'::regclass
)
-- if confrelid, conname pair shows up more than once then it is multicolumn foreign key
SELECT fk.conname as constraint_name,
fk.confrelid::regclass as referenced_table, af.attname as pkcol,
fk.conrelid::regclass as referencing_table, a.attname as fkcol
FROM foreign_keys fk
JOIN pg_attribute af ON af.attnum = fk.confkey AND af.attrelid = fk.confrelid
JOIN pg_attribute a ON a.attnum = conkey AND a.attrelid = fk.conrelid
ORDER BY fk.confrelid, fk.conname
;

正确解决问题，使用information_schema，使用多列键，在两个表中正确地连接不同名称的列，并且与ms sqlsever兼容:

select fks.TABLE_NAME as foreign_key_table_name
, fks.CONSTRAINT_NAME as foreign_key_constraint_name
, kcu_foreign.COLUMN_NAME as foreign_key_column_name
, rc.UNIQUE_CONSTRAINT_NAME as primary_key_constraint_name
, pks.TABLE_NAME as primary_key_table_name
, kcu_primary.COLUMN_NAME as primary_key_column_name
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS fks -- foreign keys
inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu_foreign -- the columns of the above keys
on fks.TABLE_CATALOG = kcu_foreign.TABLE_CATALOG
and fks.TABLE_SCHEMA = kcu_foreign.TABLE_SCHEMA
and fks.TABLE_NAME = kcu_foreign.TABLE_NAME
and fks.CONSTRAINT_NAME = kcu_foreign.CONSTRAINT_NAME
inner join INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc -- referenced constraints
on rc.CONSTRAINT_CATALOG = fks.CONSTRAINT_CATALOG
and rc.CONSTRAINT_SCHEMA = fks.CONSTRAINT_SCHEMA
and rc.CONSTRAINT_NAME = fks.CONSTRAINT_NAME
inner join INFORMATION_SCHEMA.TABLE_CONSTRAINTS pks -- primary keys (referenced by fks)
on rc.UNIQUE_CONSTRAINT_CATALOG = pks.CONSTRAINT_CATALOG
and rc.UNIQUE_CONSTRAINT_SCHEMA = pks.CONSTRAINT_SCHEMA
and rc.UNIQUE_CONSTRAINT_NAME = pks.CONSTRAINT_NAME
inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu_primary
on pks.TABLE_CATALOG = kcu_primary.TABLE_CATALOG
and pks.TABLE_SCHEMA = kcu_primary.TABLE_SCHEMA
and pks.TABLE_NAME = kcu_primary.TABLE_NAME
and pks.CONSTRAINT_NAME = kcu_primary.CONSTRAINT_NAME
and kcu_foreign.ORDINAL_POSITION = kcu_primary.ORDINAL_POSITION -- this joins the columns
where fks.TABLE_SCHEMA = 'dbo' -- replace with schema name
and fks.TABLE_NAME = 'your_table_name' -- replace with table name
and fks.CONSTRAINT_TYPE = 'FOREIGN KEY'
and pks.CONSTRAINT_TYPE = 'PRIMARY KEY'
order by fks.constraint_name, kcu_foreign.ORDINAL_POSITION

注意:在potgresql和sqlserver的information_schema实现之间存在一些差异，这使得顶部答案在两个系统上给出不同的结果——一个显示外键表的列名，另一个显示主键表的列名。出于这个原因，我决定使用KEY_COLUMN_USAGE视图。

这是我目前使用的，它将列出一个表，它的fkey约束[删除表子句，它将列出当前目录中的所有表]:

SELECT


current_schema() AS "schema",
current_catalog AS "database",
"pg_constraint".conrelid::regclass::text AS "primary_table_name",
"pg_constraint".confrelid::regclass::text AS "foreign_table_name",


(
string_to_array(
(
string_to_array(
pg_get_constraintdef("pg_constraint".oid),
'('
)
)[2],
')'
)
)[1] AS "foreign_column_name",


"pg_constraint".conindid::regclass::text AS "constraint_name",


TRIM((
string_to_array(
pg_get_constraintdef("pg_constraint".oid),
'('
)
)[1]) AS "constraint_type",


pg_get_constraintdef("pg_constraint".oid) AS "constraint_definition"


FROM pg_constraint AS "pg_constraint"


JOIN pg_namespace AS "pg_namespace" ON "pg_namespace".oid = "pg_constraint".connamespace


WHERE
--fkey and pkey constraints
"pg_constraint".contype IN ( 'f', 'p' )
AND
"pg_namespace".nspname = current_schema()
AND
"pg_constraint".conrelid::regclass::text IN ('whatever_table_name')

只需替换'您的表名'在下面的查询与您的表名。

简短但贴心的赞，如果对你有用的话。

select * from information_schema.key_column_usage
where constraint_catalog=current_catalog and table_name='your_table_name'
and position_in_unique_constraint notnull;

最快的验证直接在bash答案完全基于这个回答

IFS='' read -r -d '' sql_code << EOF_SQL_CODE
SELECT
o.oid
, o.conname AS constraint_name
, (SELECT nspname FROM pg_namespace WHERE oid=m.relnamespace) AS source_schema
, m.relname AS source_table
, (SELECT a.attname FROM pg_attribute a
WHERE a.attrelid = m.oid AND a.attnum = o.conkey[1] AND a.attisdropped = false) AS source_column
, (SELECT nspname FROM pg_namespace
WHERE oid=f.relnamespace) AS target_schema
, f.relname AS target_table
, (SELECT a.attname FROM pg_attribute a
WHERE a.attrelid = f.oid AND a.attnum = o.confkey[1] AND a.attisdropped = false) AS target_column
, ROW_NUMBER () OVER (ORDER BY o.oid) as rowid
FROM pg_constraint o
LEFT JOIN pg_class f ON f.oid = o.confrelid
LEFT JOIN pg_class m ON m.oid = o.conrelid
WHERE 1=1
AND o.contype = 'f'
AND o.conrelid IN (SELECT oid FROM pg_class c WHERE c.relkind = 'r')
EOF_SQL_CODE


psql -d my_db -c "$sql_code"

$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;

如果constraint_column_usage像key_column_usage一样有ordinal_positon列，它可以与这个列连接。所以我做了一个ordinal_position到constraint_column_usage如下所示。

我无法确认手动创建的ordinal_position与key_column_usage的顺序完全相同。但我检查了一下，至少在我的箱子里是完全一样的顺序。

SELECT
tc.table_schema,
tc.constraint_name,
tc.table_name,
kcu.column_name,
ccu.table_schema AS foreign_table_schema,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu
ON tc.constraint_name = kcu.constraint_name
AND tc.table_schema = kcu.table_schema
JOIN (select row_number() over (partition by table_schema, table_name, constraint_name order by row_num) ordinal_position,
table_schema, table_name, column_name, constraint_name
from   (select row_number() over (order by 1) row_num, table_schema, table_name, column_name, constraint_name
from   information_schema.constraint_column_usage
) t
) AS ccu
ON ccu.constraint_name = tc.constraint_name
AND ccu.table_schema = tc.table_schema
AND ccu.ordinal_position = kcu.ordinal_position
WHERE tc.constraint_type = 'FOREIGN KEY' AND tc.table_name = 'mytable'

 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。例如，使用pysql: < / p >

我自己的贡献。目标是备份所有外键的定义:

SELECT
'ALTER TABLE ' || tc.table_schema || '.' || tc.table_name || E'\n
ADD FOREIGN KEY (' || kcu.column_name || ')' || E'\n
REFERENCES ' || ccu.table_schema || '.' || ccu.table_name ||
' (' || ccu.column_name || ') ' || E'\n    ' ||
CASE WHEN rc.match_option <> 'NONE' THEN E'\n
MATCH ' || rc.match_option ELSE '' END ||
CASE WHEN rc.update_rule <> 'NO ACTION' THEN E'\n
ON UPDATE ' || rc.update_rule || ' ' ELSE '' END ||
CASE WHEN rc.delete_rule <> 'NO ACTION'
THEN 'ON DELETE ' || rc.delete_rule ELSE '' END || ';'
AS add_constraint
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu
ON tc.constraint_name = kcu.constraint_name
AND tc.table_schema = kcu.table_schema
JOIN information_schema.constraint_column_usage AS ccu
ON ccu.constraint_name = tc.constraint_name
AND ccu.table_schema = tc.table_schema
JOIN information_schema.referential_constraints AS rc
ON tc.constraint_name=rc.constraint_name
WHERE tc.constraint_type = 'FOREIGN KEY'
\t\a\g\a\ta

从最流行的答案改进查询

因为对于postgresql 12+ information_schema是非常慢的

它帮助了我:

SELECT sh.nspname AS table_schema,
tbl.relname AS table_name,
col.attname AS column_name,
referenced_sh.nspname AS foreign_table_schema,
referenced_tbl.relname AS foreign_table_name,
referenced_field.attname AS foreign_column_name
FROM pg_constraint c
INNER JOIN pg_namespace AS sh ON sh.oid = c.connamespace
INNER JOIN (SELECT oid, unnest(conkey) as conkey FROM pg_constraint) con ON c.oid = con.oid
INNER JOIN pg_class tbl ON tbl.oid = c.conrelid
INNER JOIN pg_attribute col ON (col.attrelid = tbl.oid AND col.attnum = con.conkey)
INNER JOIN pg_class referenced_tbl ON c.confrelid = referenced_tbl.oid
INNER JOIN pg_namespace AS referenced_sh ON referenced_sh.oid = referenced_tbl.relnamespace
INNER JOIN (SELECT oid, unnest(confkey) as confkey FROM pg_constraint) conf ON c.oid = conf.oid
INNER JOIN pg_attribute referenced_field ON (referenced_field.attrelid = c.confrelid AND referenced_field.attnum = conf.confkey)
WHERE c.contype = 'f'

选择的答案不为我工作，所以张贴我的sql工作。

select
con.conname as constraint_name,
src_schema.nspname as source_schema,
source.relname as source_table,
source_col.attname as source_column,
trg_schema.nspname as target_schema,
target.relname as target_table,
target_col.attname as target_column
from
pg_constraint con
inner join
pg_class source on source.oid = con.conrelid
inner join
pg_attribute source_col on source_col.attrelid = con.conrelid and source_col.attnum = con.conkey[1] and source_col.attisdropped = false
inner join
pg_namespace src_schema on src_schema.oid = source.relnamespace
inner join
pg_class target on target.oid = con.confrelid
inner join
pg_attribute target_col on target_col.attrelid = con.confrelid and target_col.attnum = con.confkey[1] and source_col.attisdropped = false
inner join
pg_namespace trg_schema on trg_schema.oid = target.relnamespace

如果有人想使用存储过程，那么这里是检索fk的方法💪

--command-1
DROP TYPE IF EXISTS returnFkType CASCADE;


--command-2
DROP FUNCTION IF EXISTS returnFks;




--command-3
CREATE TYPE returnFkType as (
constraint_name varchar,
source_schema varchar,
target_schema varchar,
source_table varchar,
target_table varchar,
source_column varchar,
target_column varchar
);


--command-4
CREATE OR REPLACE FUNCTION returnFks(_tbl varchar)
RETURNS SETOF returnFkType
LANGUAGE sql
as $$
select
c.constraint_name,
x.table_schema as source_schema,
y.table_schema as target_schema,
x.table_name as source_table,
y.table_name as target_table,
x.column_name as source_column,
y.column_name as target_column
from information_schema.referential_constraints c
join information_schema.key_column_usage x on x.constraint_name = c.constraint_name
join information_schema.key_column_usage y on y.ordinal_position = x.position_in_unique_constraint
and y.constraint_name = c.unique_constraint_name
and x.table_name = $1
order by c.constraint_name, x.ordinal_position
$$


--command-5
select * from returnFks($_TABLE);

SELECT conrelid::regclass AS table_name,
conname AS foreign_key,
pg_get_constraintdef(oid)
FROM   pg_constraint
WHERE  contype = 'f'
AND    connamespace = 'public'::regnamespace
ORDER  BY conrelid::regclass::text, contype DESC;

https://soft-builder.com/how-to-list-all-foreign-keys-in-postgresql-database