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「カスケードの削除」制約を追加する方法は？

PostgreSQL 8では、次の表の両方の外部キーを削除せずにON DELETE CASCADESを追加できますか？

# \d scores
        Table "public.scores"
 Column  |         Type          | Modifiers
---------+-----------------------+-----------
 id      | character varying(32) |
 gid     | integer               |
 money   | integer               | not null
 quit    | boolean               |
 last_ip | inet                  |
Foreign-key constraints:
   "scores_gid_fkey" FOREIGN KEY (gid) REFERENCES games(gid)
   "scores_id_fkey" FOREIGN KEY (id) REFERENCES users(id)

参照される表は両方とも以下です-ここに：

# \d games
                                     Table "public.games"
  Column  |            Type             |                        Modifiers
----------+-----------------------------+----------------------------------------------------------
 gid      | integer                     | not null default nextval('games_gid_seq'::regclass)
 rounds   | integer                     | not null
 finished | timestamp without time zone | default now()
Indexes:
    "games_pkey" PRIMARY KEY, btree (gid)
Referenced by:
    TABLE "scores" CONSTRAINT "scores_gid_fkey" FOREIGN KEY (gid) REFERENCES games(gid)

そしてここ：

# \d users
                Table "public.users"
   Column   |            Type             |   Modifiers
------------+-----------------------------+---------------
 id         | character varying(32)       | not null
 first_name | character varying(64)       |
 last_name  | character varying(64)       |
 female     | boolean                     |
 avatar     | character varying(128)      |
 city       | character varying(64)       |
 login      | timestamp without time zone | default now()
 last_ip    | inet                        |
 logout     | timestamp without time zone |
 vip        | timestamp without time zone |
 mail       | character varying(254)      |
Indexes:
    "users_pkey" PRIMARY KEY, btree (id)
Referenced by:
    TABLE "cards" CONSTRAINT "cards_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "catch" CONSTRAINT "catch_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "chat" CONSTRAINT "chat_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "game" CONSTRAINT "game_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "hand" CONSTRAINT "hand_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "luck" CONSTRAINT "luck_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "match" CONSTRAINT "match_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "misere" CONSTRAINT "misere_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "money" CONSTRAINT "money_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "pass" CONSTRAINT "pass_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "payment" CONSTRAINT "payment_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "rep" CONSTRAINT "rep_author_fkey" FOREIGN KEY (author) REFERENCES users(id)
    TABLE "rep" CONSTRAINT "rep_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "scores" CONSTRAINT "scores_id_fkey" FOREIGN KEY (id) REFERENCES users(id)
    TABLE "status" CONSTRAINT "status_id_fkey" FOREIGN KEY (id) REFERENCES users(id)

また、前のテーブルに2つのインデックスを追加するのが理にかなっているのだろうか？

PDATE：ありがとう

ALTER TABLE public.scores
DROP CONSTRAINT scores_gid_fkey,
ADD CONSTRAINT scores_gid_fkey
   FOREIGN KEY (gid)
   REFERENCES games(gid)
   ON DELETE CASCADE;
postgresqlconstraintscascadecascading-deletespostgresql-8.4
145
Alexander Farber

既存の外部キー制約にon delete cascadeを単純に追加することはできないと確信しています。最初に制約を削除してから、正しいバージョンを追加する必要があります。標準SQLでは、これを行う最も簡単な方法は

  • トランザクションを開始し、
  • 外部キーをドロップし、
  • on delete cascadeで外部キーを追加し、最後に
  • トランザクションをコミットする

変更する外部キーごとに繰り返します。

ただし、PostgreSQLには、単一のSQLステートメントで複数の制約句を使用できる非標準の拡張機能があります。例えば

alter table public.scores
drop constraint scores_gid_fkey,
add constraint scores_gid_fkey
   foreign key (gid)
   references games(gid)
   on delete cascade;

削除する外部キー制約の名前がわからない場合は、pgAdminIIIで検索できます（テーブル名をクリックしてDDLを確認するか、「制約」が表示されるまで階層を展開します）。または、 情報スキーマのクエリ を使用できます。

select *
from information_schema.key_column_usage
where position_in_unique_constraint is not null
185
Mike Sherrill 'Cat Recall'

@Mike Sherrill Cat Recallの回答に基づいて、これは私にとってうまくいったものです：

ALTER TABLE "Children"
DROP CONSTRAINT "Children_parentId_fkey",
ADD CONSTRAINT "Children_parentId_fkey"
  FOREIGN KEY ("parentId")
  REFERENCES "Parent"(id)
  ON DELETE CASCADE;
4
Fellow Stranger

使用法：

select replace_foreign_key('user_rates_posts', 'post_id', 'ON DELETE CASCADE');

関数：

CREATE OR REPLACE FUNCTION 
    replace_foreign_key(f_table VARCHAR, f_column VARCHAR, new_options VARCHAR) 
RETURNS VARCHAR
AS $$
DECLARE constraint_name varchar;
DECLARE reftable varchar;
DECLARE refcolumn varchar;
BEGIN

SELECT tc.constraint_name, 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
    JOIN information_schema.constraint_column_usage AS ccu
      ON ccu.constraint_name = tc.constraint_name
WHERE constraint_type = 'FOREIGN KEY' 
   AND tc.table_name= f_table AND kcu.column_name= f_column
INTO constraint_name, reftable, refcolumn;

EXECUTE 'alter table ' || f_table || ' drop constraint ' || constraint_name || 
', ADD CONSTRAINT ' || constraint_name || ' FOREIGN KEY (' || f_column || ') ' ||
' REFERENCES ' || reftable || '(' || refcolumn || ') ' || new_options || ';';

RETURN 'Constraint replaced: ' || constraint_name || ' (' || f_table || '.' || f_column ||
 ' -> ' || reftable || '.' || refcolumn || '); New options: ' || new_options;

END;
$$ LANGUAGE plpgsql;

注意：この関数コピーしない初期外部キーの属性。外部テーブル名/列名のみを取り、現在のキーを削除し、replacesを新しいキーに置き換えます。

3
Daniel Garmoshka