问题
This question was originally asked by @PrateekGupta
Background
@PrateekGupta wanted to perform bulk insert operation on multiple tables.
The tables have foreign key relationships between themselves.
If an INSERT operation is done on a table with a foreign key before the referenced table is being inserted to, the operation might fail due to violation of the foreign key.
Requirement
Produce a list of tables within a database ordered according to their dependencies.
Tables with no dependencies (no foreign keys) will be 1st.
Tables with dependencies only in the 1st set of tables will be 2nd.
Tables with dependencies only in the 1st or 2nd sets of tables will be 3rd.
and so on...
回答1:
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
;
回答2:
Thanks for David.
I've just added the schema name to his query if anyone needed
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;
回答3:
I needed to do this myself and was hoping someone had already done it for Postgres, but didn't find anything, so I'll just leave this here:
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;
This is a bit of a hybrid query between two use cases. You may remove the GROUP BY and SELECT source::regclass instead, if you need to see to which table the foreign key refers.
回答4:
The Oracle version of the script:
with
foreign_keys as (
select
src_cc.owner as src_owner,
src_cc.table_name as src_table,
src_cc.column_name as src_column,
dest_cc.owner as dest_owner,
dest_cc.table_name as dest_table,
dest_cc.column_name as dest_column,
c.constraint_name
from
all_constraints c
inner join all_cons_columns dest_cc on
c.r_constraint_name = dest_cc.constraint_name
and c.r_owner = dest_cc.owner
inner join all_cons_columns src_cc on
c.constraint_name = src_cc.constraint_name
and c.owner = src_cc.owner
where
c.constraint_type = 'R'
and dest_cc.owner = :owner),
cte (lvl,table_name) as (
select 1, table_name
from all_tables
where
owner = :owner
union all
select cte.lvl + 1, t.table_name
from cte
join all_tables t on exists (
select null
from foreign_keys fk
where
fk.src_table = t.table_name
and fk.dest_table = cte.table_name
)
and t.table_name <> cte.table_name
AND cte.lvl < 30
)
select table_name, max (lvl) as dependency_level
from cte
group by table_name
order by dependency_level desc, table_name
;
来源：https://stackoverflow.com/questions/40388903/how-to-list-tables-in-their-dependency-order-based-on-foreign-keys