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
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%'
其他回答
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'
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%'
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(或者是搜索路径中的第一个),则对表名进行模式限定:
WHERE r.conrelid = 'myschema.mytable'::regclass
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'
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
推荐文章
- 如何在Ruby On Rails中使用NuoDB手动执行SQL命令
- 查询JSON类型内的数组元素
- 确定记录是否存在的最快方法
- 获得PostgreSQL数据库中当前连接数的正确查询
- 在SQL选择语句Order By 1的目的是什么?
- 我如何循环通过一组记录在SQL Server?
- 纬度和经度的数据类型是什么?
- 如何在PostgreSQL中临时禁用触发器?
- 如何从命令行通过mysql运行一个查询?
- 外键约束可能导致循环或多条级联路径?
- 输入文件似乎是一个文本格式转储。请使用psql
- 使用LIMIT/OFFSET运行查询,还可以获得总行数
- 当恢复sql时,psql无效命令\N
- 货币应该使用哪种数据类型?
- 如何选择每一行的列值不是独特的