blocks|key|1034213|text|Postgres外键支持级联删除：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1034214|slice_id+integer+REFERENCES+slice(id)+ON+DELETE+CASCADE|code-block|syntax|javascript|1034215|等|1034216|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Postgres foreign keys support the CASCADE deletes:

<pre><code>slice_id integer REFERENCES slice(id) ON DELETE CASCADE
</code></pre>

etc

blocks|key|4440312|text|以防你不能按照别人的建议去做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4440313|begin;
delete+from+classification_item+where+transaction_id+in+(select+id+from+"transaction"+where+slice_id+=+(select+id+from+slice+where+name+=+'my_slice'));
delete+from+"transaction"+where+slice_id+in+(select+id+from+slice+where+name='my_slice');
delete+from+slice+where+name='my_slice';
commit;|code-block|syntax|javascript|4440314|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In case you can't do what others have suggested:

<pre><code>begin;
delete from classification_item where transaction_id in (select id from "transaction" where slice_id = (select id from slice where name = 'my_slice'));
delete from "transaction" where slice_id in (select id from slice where name='my_slice');
delete from slice where name='my_slice';
commit;
</code></pre>

blocks|key|1777687|text|它是在表中定义的东西，而不是DELETE查询。示例(查看order_id)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1777688|CREATE+TABLE+order_items+(
++++product_no+integer+REFERENCES+products+ON+DELETE+RESTRICT,
++++order_id+integer+REFERENCES+orders+ON+DELETE+CASCADE,
++++quantity+integer,
++++PRIMARY+KEY+(product_no,+order_id)
);|code-block|syntax|javascript|1777689|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

It's soemthing that is defined in the table rather than the DELETE Query. Example (look at order_id):

<pre><code>CREATE TABLE order_items (
 product_no integer REFERENCES products ON DELETE RESTRICT,
 order_id integer REFERENCES orders ON DELETE CASCADE,
 quantity integer,
 PRIMARY KEY (product_no, order_id)
);
</code></pre>

blocks|key|4440409|text|您应该使用级联删除，即使您继承了数据库架构，也应该可以这样做。您只需修改约束，将级联删除添加到模式中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4440410|4440411|删除并重新创建约束以添加级联删除：|ordered-list-item|4440412|4440413|ALTER+TABLE+ONLY+"transaction“DROP+CONSTRAINT+transaction_slice_id_fkey；ALTER+TABLE+ONLY+"transaction”在DELETE+CASCADE上添加约束transaction_slice_id_fkey外键(slice_id)引用切片(Id)；ALTER+TABLE+ONLY+"classification_item“DROP+CONSTRAINT+classification_item_transaction_id_fkey；ALTER+TABLE+ONLY+"classification_item”ADD+CONSTRAINT+classification_item_transaction_id_fkey+FOREIGN+KEY+(transaction_id)在DELETE+CASCADE上引用事务(Id)；|4440414|现在，以下查询不仅会从表slice中删除my_slice记录，还会从表transaction和classification_item中删除引用该记录的所有记录：|unordered-list-item|offset|length|style|CODE|4440415|4440416|从切片中删除WHERE+name='my_slice';|4440417|即使原始模式是由像SQLAlchemy这样的对象关系映射器创建的，这个过程也是有效的。但是，在这种情况下，请注意在模式更改或重新创建时重新应用“补丁程序”。只有在不能自动实现的情况下，这毕竟不是一个好主意…|4440418|entityMap^0|0|0|0|0|0|C|5|K|8|Z|B|1B|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Y|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|11|8|@$L|12|M|13|N|O]|$L|14|M|15|N|O]|$L|16|M|17|N|O]|$L|18|M|19|N|O]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1C|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|V|$]]

You should use CASCADE deletes, and it should be possible to do so even if you inherited a database schema. You would just modify the constraints to add the CASCADE deletes to the schemas:

<ol>
<li>Drop and re-create the constraints to add CASCADE deletes:

<pre><code>ALTER TABLE ONLY "transaction" 
 DROP CONSTRAINT transaction_slice_id_fkey;
ALTER TABLE ONLY "transaction" 
 ADD CONSTRAINT transaction_slice_id_fkey 
 FOREIGN KEY (slice_id) REFERENCES slice(id) ON DELETE CASCADE;

ALTER TABLE ONLY "classification_item" 
 DROP CONSTRAINT classification_item_transaction_id_fkey;
ALTER TABLE ONLY "classification_item" 
 ADD CONSTRAINT classification_item_transaction_id_fkey 
 FOREIGN KEY (transaction_id) REFERENCES transaction(id) ON DELETE CASCADE;
</code></pre></li>
<li>Now the following query will delete not just the <code>my_slice</code> record from table <code>slice</code>, but also all records from tables<code>transaction</code> and <code>classification_item</code> referencing it:

<pre><code>DELETE FROM slice WHERE name='my_slice';
</code></pre></li>
</ol>

That procedure will work even if the original schema is created by an object-relational mapper like SQLAlchemy. However in such a case, take care to re-apply that "patch" whenever the schema changes or is re-created. Only if that can't be implemented automatically, it might not be a good idea after all …

blocks|key|1777729|text|通过设置约束属性'On+delete‘=+CASCADE，可以将其委托给DBMS。请参阅an+example。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1777730|entityMap|0|LINK|mutability|MUTABLE|url|https://i.stack.imgur.com/2Cgjs.png^0|18|A|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

It can be delegated to DBMS by set a constraint property 'On delete' = CASCADE. Please see <a href="https://i.stack.imgur.com/2Cgjs.png" rel="nofollow noreferrer">an example</a>.

I'm manually constructing a DELETE CASCADE statement for postgres.

I have a 'transaction' and a 'slice' table, related as shown below:

<pre><code> Table "public.slice"
 Column | Type | Modifiers 
----------+------+-----------
 id | text | not null
 name | text | 
Referenced by:
 TABLE "transaction" CONSTRAINT "transaction_slice_id_fkey" FOREIGN KEY (slice_id) REFERENCES slice(id)
 Table "public.transaction"
 Column | Type | Modifiers 
----------+------+-----------
 id | text | not null
 slice_id | text | 
Referenced by:
 TABLE "classification_item" CONSTRAINT "classification_item_transaction_id_fkey" FOREIGN KEY (transaction_id) REFERENCES transaction(id)
Table "public.classification_item"
 Column | Type | Modifiers 
----------------+------+-----------
 id | text | not null
 transaction_id | text | 
Foreign-key constraints:
 "classification_item_transaction_id_fkey" FOREIGN KEY (transaction_id) REFERENCES transaction(id)
</code></pre>

Say I want to delete all transactions and classification_items referenced by the slice whose name is 'my_slice'. What do I need to write?

<pre><code>=# delete from classification_item where transaction_id= #...? 
=# delete from transaction where slice_id= #...? 
=# delete from slice where name='my_slice';
</code></pre>

How does one write a DELETE CASCADE for postgres?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在为postgres手动构造一个DELETE CASCADE语句。我有一个'transaction‘和一个'slice’表，相关如下所示：    Table "public.slice"  Column  | Type | Modifiers ----------+------+----------- id    ...

问如何为postgres编写删除级联？
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问如何为postgres编写删除级联？EN