这个问题最初是由@PrateekGupta提出的
@PrateekGupta想要对多个表执行批量插入操作。 表格之间有外键关系。 如果在插入引用的表之前对具有外键的表执行INSERT操作,则操作可能由于违反外键而失败。
生成根据其依赖关系排序的数据库中的表列表。 没有依赖关系的表(没有外键)将是第1个。 仅在第1组表中具有依赖关系的表将是第2个。 仅在第1或第2组表中具有依赖关系的表将是第3个。 等等...
example:
create table t1 (i int primary key,j int unique)
create table t2 (i int primary key references t1 (i));
create table t3 (i int,j int,primary key (i,j));
create table t4 (i int,j int, foreign key (i,j) references t3 (i,j));
create table t5 (i int references t1 (i),j int,foreign key (i,j) references t3 (i,j));
create table t6 (i int references t2 (i));
with cte (lvl,object_id,name)
as
(
select 1
,object_id
,name
from sys.tables
where type_desc = 'USER_TABLE'
and is_ms_shipped = 0
union all
select cte.lvl + 1
,t.object_id
,t.name
from cte
join sys.tables as t
on exists
(
select null
from sys.foreign_keys as fk
where fk.parent_object_id = t.object_id
and fk.referenced_object_id = cte.object_id
)
and t.object_id <> cte.object_id
and cte.lvl < 30
where t.type_desc = 'USER_TABLE'
and t.is_ms_shipped = 0
)
select name
,max (lvl) as dependency_level
from cte
group by name
order by dependency_level
,name
;
谢谢大卫。
如果有人需要,我刚刚将模式名称添加到他的查询中
WITH cte (lvl, object_id, name, schema_Name) AS
(SELECT 1, object_id, sys.tables.name, sys.schemas.name as schema_Name
FROM sys.tables Inner Join sys.schemas on sys.tables.schema_id = sys.schemas.schema_id
WHERE type_desc = 'USER_TABLE'
AND is_ms_shipped = 0
UNION ALL SELECT cte.lvl + 1, t.object_id, t.name, S.name as schema_Name
FROM cte
JOIN sys.tables AS t ON EXISTS
(SELECT NULL FROM sys.foreign_keys AS fk
WHERE fk.parent_object_id = t.object_id
AND fk.referenced_object_id = cte.object_id )
JOIN sys.schemas as S on t.schema_id = S.schema_id
AND t.object_id <> cte.object_id
AND cte.lvl < 30
WHERE t.type_desc = 'USER_TABLE'
AND t.is_ms_shipped = 0 )
SELECT schema_Name, name, MAX (lvl) AS dependency_level
FROM cte
GROUP BY schema_Name, name
ORDER BY dependency_level,schema_Name, name;
我需要自己做这件事并且希望有人已经为Postgres做了这件事,但没有找到任何东西,所以我将把它留在这里:
WITH RECURSIVE t AS (
SELECT relnamespace as nsp, oid as tbl, null::regclass as source, 1 as level
FROM pg_class
WHERE relkind = 'r'
AND relnamespace not in ('pg_catalog'::regnamespace, 'information_schema'::regnamespace)
UNION ALL
SELECT c.connamespace as nsp, c.conrelid as tbl, c.confrelid as source, p.level + 1
FROM pg_constraint c
INNER JOIN t p ON (c.confrelid = p.tbl AND c.connamespace = p.nsp)
WHERE c.contype = 'f'
AND c.connamespace not in ('pg_catalog'::regnamespace, 'information_schema'::regnamespace)
)
SELECT nsp::regnamespace, tbl::regclass
FROM t
GROUP BY nsp, tbl
ORDER BY max(level) DESC;
这是两个用例之间的混合查询。如果你需要查看外键所指的表,你可以删除GROUP BY
和SELECT source::regclass
。