Create FOREIGN KEY : FOREIGN KEY « Constraints « PostgreSQL

1. PostgreSQL
2. Constraints
3. FOREIGN KEY

Create FOREIGN KEY

postgres=#
postgres=# CREATE TABLE "books" (
postgres(#      "id"           integer NOT NULL,
postgres(#      "title"        text NOT NULL,
postgres(#      "author_id"    integer,
postgres(#      "subject_id"   integer,
postgres(#      Constraint "books_id_pkey" Primary Key ("id")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE editions
postgres-#               (isbn text,
postgres(#               book_id integer,
postgres(#               edition integer,
postgres(#               publisher_id integer,
postgres(#               publication date,
postgres(#               type char,
postgres(#               CONSTRAINT pkey PRIMARY KEY (isbn),
postgres(#               CONSTRAINT integrity CHECK (book_id IS NOT NULL
postgres(#                                           AND edition IS NOT NULL),
postgres(#               CONSTRAINT book_exists FOREIGN KEY (book_id)
postgres(#                          REFERENCES books (id)
postgres(#                          ON DELETE CASCADE
postgres(#                          ON UPDATE CASCADE);
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "pkey" for table "editions"
CREATE TABLE
postgres=#
postgres=# drop table books cascade;
NOTICE:  drop cascades to constraint book_exists on table editions
DROP TABLE
postgres=# drop table editions cascade;
DROP TABLE
postgres=#
           
       

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