Adding a constraint to an existing table: add foreign key to table : FOREIGN KEY « Constraints « PostgreSQL






  1. PostgreSQL
  2. Constraints
  3. FOREIGN KEY

Adding a constraint to an existing table: add foreign key to table


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=# -- Adding a constraint to an existing table
postgres=#
postgres=# ALTER TABLE books ADD CONSTRAINT legal_subjects
postgres-#                    FOREIGN KEY (subject_id)
postgres-#                    REFERENCES subjects (id);
ALTER TABLE
postgres=#
postgres=# drop table books;
DROP TABLE
postgres=#








Related examples in the same category

1.Define foreign key for a table
2.Reference two two columns as foreign key column
3.Adding constraints (FOREIGN KEY) to a table
4.Create FOREIGN KEY
5.Using foreign keys
6.ALTER TABLE employee ADD FOREIGN KEY (group_id) REFERENCES product_groups