Question

我有三个表：A，B和C.我想创建表A，它应该有3列，第一列应该是PRIMARY KEY。

1）如何创建第二列，是对表B的引用，

2）和第三个是对表C中'C.id'行的引用.A.id = C.id

CREATE TABLE A
(
    id SERIAL PRIMARY KEY,
    // ? - reference to table B
    // ? - reference to C.id row. A.id = C.id
)

数据库：postgresql

Answer 1

我假设您使用的是mysql数据库。

CREATE TABLE A
(
    id INT NOT NULL PRIMARY KEY,
    b_id INT NOT NULL,
    c_id INT NOT NULL,
    FOREIGN KEY (b_id) REFERENCES B (id),
    FOREIGN KEY (c_id) REFERENCES C (id)
) TYPE = INNODB;

使用postgresql的更新：

CREATE TABLE "A"
(
   id integer NOT NULL, 
   b_id integer NOT NULL, 
   c_id integer NOT NULL, 
   CONSTRAINT id PRIMARY KEY (id), 
   CONSTRAINT b_id FOREIGN KEY (b_id) REFERENCES "B" (id) 
      ON UPDATE NO ACTION ON DELETE NO ACTION, --with no action restriction
   CONSTRAINT c_id FOREIGN KEY (c_id) REFERENCES "C" (id) 
      ON UPDATE CASCADE ON DELETE CASCADE  --with cascade restriction
) 
WITH (
  OIDS = FALSE
)
;
ALTER TABLE "C" OWNER TO postgres;

从一个表引用到另一个整个表和指定的行

1 个答案:

使用postgresql的更新：