ER 图
- ER diagrama, entidade também conhecida - Contato diagrama (Diagrama Entidade Relacionamento), ele fornece uma maneira para representar os tipos de entidades, atributos e links, para descrever o modelo de relacionamento entidade conceitual da realidade.
- FIG ER em entidades, atributos, relações três componentes principais.
- ER diagrama da relação em três, um a um, de um para muitos, muitos para muitos.
ER diagrama abaixo para um processo comercial, por exemplo, em conjunto com a instrução SQL correspondente (deficiências aceites apontando).
TABLE construída:
--用户表
CREATE TABLE pleatuser(
id VARCHAR2(32),
user_name VARCHAR2(32) NOT NULL,
user_addr VARCHAR2(64) DEFAULT '该用户很懒,没有填写地址',
phone VARCHAR2(11) UNIQUE,
CONSTRAINT pk_pleatuser_id PRIMARY KEY(id)
);
--添加备注
COMMENT ON TABLE pleatuser.id IS '用户id';
COMMENT ON TABLE pleatuser.user_name IS '用户名称';
COMMENT ON TABLE pleatuser.user_addr IS '用户地址';
COMMENT ON TABLE pleatuser.phone IS '用户电话';
--订单表
CREATE TABLE indent(
id VARCHAR2(32),
user_id VARCHAR2(32) UNIQUE NOT NULL,
commodity_id VARCHAR2(32) UNIQUE NOT NULL,
create_date DATE,
CONSTRAINT pk_indent_id PRIMARY KEY(id),
CONSTRAINT fk_pleatuser_indent FOREIGN KEY(user_id) REFERENCES pleatuser(id)
);
COMMENT ON TABLE indent.id IS '订单id';
COMMENT ON TABLE indent.user_id IS '用户id';
COMMENT ON TABLE indent.commodity_id IS '商品id';
COMMENT ON TABLE indent.create_date IS '下单时间';
--订单详情表
CREATE TABLE indentdetail(
id VARCHAR2(32),
indent_id VARCHAR2(32) UNIQUE NOT NULL,
commodity_id VARCHAR(32) UNIQUE NOT NULL,
CONSTRAINT pk_indentdetail_id PRIMARY KEY(id),
CONSTRAINT fk_indent_indentdetail FOREIGN KEY(indent_id) REFERENCES indent(id),
CONSTRAINT fk_commodity_indentdetail FOREIGN KEY(commodity_id) REFERENCES commodity(id)
);
COMMENT ON TABLE indentdetail.id IS '订单详情id';
COMMENT ON TABLE indentdetail.ident_id IS '订单id';
COMMENT ON TABLE indentdetail.commodity IS '商品id';
--浏览记录表
CREATE TABLE browse(
id VARCHAR2(32),
user_id VARCHAR2(32) UNIQUE NOT NULL,
commodity_id VARCHAR2(32) UNIQUE NOT NULL,
browse_date DATE,
CONSTRAINT pk_browse_id PRIMARY KEY(id),
constraint fk_browsse_commodity FOREIGN KEY(commodity_id) REFERENCES commodity(id),
constraint fk_browse_pleatuser FOREIGN KEY(user_id) REFERENCES pleatuser(id)
);
COMMENT ON TABLE browse.id IS '浏览记录id';
COMMENT ON TABLE browse.user_id IS '浏览用户id';
COMMENT ON TABLE browse.commodity_id IS '浏览的商品id';
COMMENT ON TABLE browse.create_date IS '浏览时间';
--商品表
CREATE TABLE commodity(
id VARCHAR2(32),
commodity_name VARCHAR2(64) NOT NULL,
category VARCHAR2(32) DEFAULT '生活',
CONSTRAINT pk_commodity_id PRIMARY KEY(id)
);
COMMENT ON TABLE commodity.id IS '商品id';
COMMENT ON TABLE commodity.commodity_name IS '商品名称';
COMMENT ON TABLE commodity.category IS '商品类别';
--商家表
CREATE TABLE merchant(
id VARCHAR2(32),
merchant_name VARCHAR2(32) NOT NULL,
merchant_addr VARCHAR2(64) DEFAULT '商家很懒,没有填写地址',
CONSTRAINT pk_merchant_id PRIMARY KEY(id)
);
COMMENT ON TABLE merchant.id IS '商家id';
COMMENT ON TABLE merchant.merchant_name IS '商家名称';
COMMENT ON TABLE merchant.merchant_addr IS '商家地址';
--截断表(清除表数据,不能回滚)
TRUNCATE TABLE PLEATUSER;
--删除表
DROP TABLE PLEATUSER;
TRUNCATE TABLE INDENT;
DROP TABLE INDENT;
TRUNCATE TABLE INDETNDETAIL;
DROP TABLE INDETNDETAIL;
TRUNCATE TABLE BROWSE;
DROP TABLE BROWSE;
TRUNCATE TABLE COMMODITY;
DROP TABLE COMMODITY;
TRUNCATE TABLE MERCHANT;
DROP TABLE MERCHANT;
Ao estudar os registros, se as deficiências boas-vindas a mensagem que aponta ...