是否有一种方法使用SQL列出给定表的所有外键?我知道表名/模式,我可以把它插入。
当前回答
我升级了@ollyc的答案,目前在顶部。 我同意@fionbio,因为key_column_usage和constraint_column_usage在列级上没有相关信息。
如果constraint_column_usage具有像key_column_usage一样的ordinal_position列,则可以将其与该列连接。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'
其他回答
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。
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');
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'
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
在PostgreSQL提示符上发出\d+ tablename,除了显示表列的数据类型外,它还会显示索引和外键。
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