[英]How can I find tables which reference a particular row via a foreign key?
Given a structure like this: 给定这样的结构:
CREATE TABLE reference_table (
reference_table_key numeric NOT NULL,
reference_value numeric,
CONSTRAINT reference_table_pk PRIMARY KEY (reference_table_key)
);
CREATE TABLE other_table (
other_table_key numeric NOT NULL,
reference_table_key numeric,
CONSTRAINT other_table_pk PRIMARY KEY (other_table_key),
ONSTRAINT other_table_reference_fk FOREIGN KEY (reference_table_key)
REFERENCES reference_table (reference_table_key) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE SET NULL
);
CREATE TABLE another_table (
another_table_key numeric NOT NULL,
do_stuff_key numeric,
CONSTRAINT another_table_pk PRIMARY KEY (another_table_key),
ONSTRAINT another_table_reference_fk FOREIGN KEY (do_stuff_key)
REFERENCES reference_table (reference_table_key) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE SET NULL
);
--there are 50-60 tables which have similar foreign key references to reference_table
I want to write a query that tells me the primary keys in other_table and another_table and potentially more tables where reference_value is NULL. 我想编写一个查询,告诉我other_table和another_table中的主键以及reference_value为NULL的更多表。
In psuedo-code: 在伪代码中:
SELECT table_name, table_primary_key, table_fk_column_name
FROM ?????? some PG table ???????, reference_table
WHERE reference_table.reference_value IS NULL;
The result would look something like: 结果如下所示:
table_name | table_primary_key | table_fk_column_name | reference_table_pk
---------------------------------------------------------------------------
other_table | 2 | reference_table_key | 7
other_table | 4 | reference_table_key | 56
other_table | 45 | reference_table_key | 454
other_table | 65765 | reference_table_key | 987987
other_table | 11 | reference_table_key | 3213
another_table | 3 | do_stuff_key | 4645
another_table | 5 | do_stuff_key | 43546
another_table | 7 | do_stuff_key | 464356
unknown_table | 1 | unkown_column_key | 435435
unknown_table | 1 | some_other_column_key | 34543
unknown_table | 3 | unkown_column_key | 124
unknown_table | 3 | some_other_column_key | 123
This is similar to, but not a duplicate of Postgres: SQL to list table foreign keys . 这类似于但不是Postgres的重复:SQL列出表外键 。 That question shows the table structure.
这个问题说明了表的结构。 I want to find specific instances.
我想找到特定的实例。
Essentially if I were to DELETE FROM reference_table WHERE reference_value IS NULL;
本质上,如果我
DELETE FROM reference_table WHERE reference_value IS NULL;
, postgres has to do something internally to figure out that it needs to set reference_table_key
in row 2 in other_table
to NULL. ,Postgres的有做一些内部找出它需要一套
reference_table_key
在第2行中other_table
为NULL。 I want to see what those rows would be. 我想看看这些行是什么。
Is there a query that can do this? 有查询可以做到这一点吗? Is there a modifier that I can pass to a DELETE call that would tell me what tables/rows/columns would be affected by that DELETE?
有没有可以传递给DELETE调用的修饰符,可以告诉我该DELETE将影响哪些表/行/列?
This query produces the DML statement to find all rows in all tables, where a column has a foreign-key constraint referencing another table but hold a NULL
value in that column: 此查询生成DML语句以查找所有表中的所有行 ,其中一列具有引用另一个表的外键约束,但在该列中保留
NULL
值:
WITH x AS (
SELECT c.conrelid::regclass AS tbl
, c.confrelid::regclass AS ftbl
, quote_ident(k.attname) AS fk
, quote_ident(pf.attname) AS pk
FROM pg_constraint c
JOIN pg_attribute k ON (k.attrelid, k.attnum) = (c.conrelid, c.conkey[1])
JOIN pg_attribute f ON (f.attrelid, f.attnum) = (c.confrelid, c.confkey[1])
LEFT JOIN pg_constraint p ON p.conrelid = c.conrelid AND p.contype = 'p'
LEFT JOIN pg_attribute pf ON (pf.attrelid, pf.attnum)
= (p.conrelid, p.conkey[1])
WHERE c.contype = 'f'
AND c.confrelid = 'fk_tbl'::regclass -- references to this tbl
AND f.attname = 'fk_tbl_id' -- and only to this column
)
SELECT string_agg(format(
'SELECT %L AS tbl
, %L AS pk
, %s::text AS pk_val
, %L AS fk
, %L AS ftbl
FROM %1$s WHERE %4$s IS NULL'
, tbl
, COALESCE(pk 'NONE')
, COALESCE(pk 'NULL')
, fk
, ftbl), '
UNION ALL
') || ';'
FROM x;
Produces a query like this: 产生这样的查询:
SELECT 'some_tbl' AS tbl
, 'some_tbl_id' AS pk
, some_tbl_id::text AS pk_val
, 'fk_tbl_id' AS fk
, 'fk_tbl' AS ftbl
FROM some_tbl WHERE fk_tbl_id IS NULL
UNION ALL
SELECT 'other_tbl' AS tbl
, 'other_tbl_id' AS pk
, other_tbl_id::text AS pk_val
, 'some_name_id' AS fk
, 'fk_tbl' AS ftbl
FROM other_tbl WHERE some_name_id IS NULL;
Produces output like this: 产生如下输出:
tbl | pk | pk_val | fk | ftbl
-----------+--------------+--------+--------------+--------
some_tbl | some_tbl_id | 49 | fk_tbl_id | fk_tbl
some_tbl | some_tbl_id | 58 | fk_tbl_id | fk_tbl
other_tbl | other_tbl_id | 66 | some_name_id | fk_tbl
other_tbl | other_tbl_id | 67 | some_name_id | fk_tbl
Does not cover multi-column foreign or primary keys reliably . 不能可靠地覆盖多列外键或主键 。 You have to make the query more complex for this.
您必须为此使查询更复杂。
I cast all primary key values to text
to cover all types. 我投所有的主键值
text
涵盖所有类型。
Adapt or remove these lines to find foreign key pointing to an other or any column / table: 调整或删除这些行,以找到指向另一个或任何列/表的外键:
AND c.confrelid = 'fk_tbl'::regclass AND f.attname = 'fk_tbl_id' -- and only this column
Tested with PostgreSQL 9.1.4. 已在PostgreSQL 9.1.4中测试。 I use the
pg_catalog
tables. 我使用
pg_catalog
表。 Realistically nothing of what I use here is going to change, but that is not guaranteed across major releases. 实际上,我在这里使用的所有内容都不会改变,但这在主要版本中不能保证。 Rewrite it with tables from
information_schema
if you need it to work reliably across updates. 如果您需要它在更新中可靠地工作,请使用
information_schema
表重写它。 That is slower, but sure. 那比较慢,但是可以肯定。
I did not sanitize table names in the generated DML script, because quote_ident()
would fail with schema-qualified names. 我没有在生成的DML脚本中
quote_ident()
表名,因为quote_ident()
会因架构限定名而失败。 It is your responsibility to avoid harmful table names like "users; DELETE * FROM users;"
您有责任避免使用有害的表名,例如
"users; DELETE * FROM users;"
. 。 With some more effort, you can retrieve schema-name and table name separately and use
quote_ident()
. 花费更多的精力,您可以分别检索架构名称和表名称,并使用
quote_ident()
。
My first solution does something subtly different from what you ask, because what you describe (as I understand it) is non-existent. 我的第一个解决方案与您的要求有一些细微的差别,因为您所描述的(根据我的理解)不存在。 The value
NULL
is "unknown" and cannot be referenced. 值
NULL
为“未知”,无法引用。 If you actually want to find rows with a NULL
value in a column that has FK constraints pointing to it (not to the particular row with the NULL
value, of course), then the query can be much simplified: 如果你真的想找到一个行
NULL
在具有FK约束指向它(不特定的行与列值NULL
值,当然),那么查询可以大大简化:
WITH x AS (
SELECT c.confrelid::regclass AS ftbl
,quote_ident(f.attname) AS fk
,quote_ident(pf.attname) AS pk
,string_agg(c.conrelid::regclass::text, ', ') AS referencing_tbls
FROM pg_constraint c
JOIN pg_attribute f ON (f.attrelid, f.attnum) = (c.confrelid, c.confkey[1])
LEFT JOIN pg_constraint p ON p.conrelid = c.confrelid AND p.contype = 'p'
LEFT JOIN pg_attribute pf ON (pf.attrelid, pf.attnum)
= (p.conrelid, p.conkey[1])
WHERE c.contype = 'f'
-- AND c.confrelid = 'fk_tbl'::regclass -- only referring this tbl
GROUP BY 1, 2, 3
)
SELECT string_agg(format(
'SELECT %L AS ftbl
, %L AS pk
, %s::text AS pk_val
, %L AS fk
, %L AS referencing_tbls
FROM %1$s WHERE %4$s IS NULL'
, ftbl
, COALESCE(pk, 'NONE')
, COALESCE(pk, 'NULL')
, fk
, referencing_tbls), '
UNION ALL
') || ';'
FROM x;
Finds all such rows in the entire database (commented out the restriction to one table). 在整个数据库中查找所有此类行(注释了对一个表的限制)。 Tested with Postgres 9.1.4 and works for me.
经过Postgres 9.1.4测试并为我工作。
I group multiple tables referencing the same foreign column into one query and add a list of referencing tables to give an overview. 我将多个引用同一外来列的表分组到一个查询中,并添加了一个引用表列表以进行概述。
You want a union for this query: 您需要此查询的联合:
select *
from ((select 'other_table' as table_name,
other_table_key as primary_key,
'reference_table_key' as table_fk,
ot.reference_table_key
from other_table ot left outer join
reference_table rt
on ot.reference_table_key = rt.reference_table_key
where rt.reference_value is null
) union all
(select 'another_table' as table_name,
another_table_key as primary_key,
'do_stuff_key' as table_fk,
at.do_stuff_key
from another_table at left outer join
reference_table rt
on at.do_stuff_key = rt.reference_table_key
where rt.reference_value is null
)
) t
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