如何添加"on delete cascade“约束？
如何添加"on delete cascade“约束？
提问于 2012-04-28 03:09:47
在PostgreSQL 8中，是否可以将ON DELETE CASCADES添加到下表中的两个外键，而不删除后者？
# \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)两个被引用的表格如下-此处：
# \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)还有这里：
# \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)我还想知道在以前的表中添加2个索引是否有意义？
更新：谢谢你，我在邮件列表上得到了建议，我可以用一条语句来管理它，因此不需要显式地启动一个事务：
ALTER TABLE public.scores
DROP CONSTRAINT scores_gid_fkey,
ADD CONSTRAINT scores_gid_fkey
FOREIGN KEY (gid)
REFERENCES games(gid)
ON DELETE CASCADE;页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/10356484
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