Question

嘿，所以我试图向我的数据库添加支票。我目前正在创建一个用于租车的MySQL数据库（这是一个用于大学的项目），我的约束是，只有他们有驾驶员编号的情况下，该人才是批准的客户，所以...

CREATE TABLE  customers  (
   customer_id  int(50) UNSIGNED ZEROFILL NOT NULL,
   fname  varchar(20) NOT NULL,
   lname  varchar(20) NOT NULL,
   address  varchar(30) NOT NULL,
   city  varchar(20) NOT NULL,
   county  ENUM('Armagh','Carlow','Cavan','Clare','Cork','Derry','Donegal','Down','Dublin','Fermanagh','Galway','Kerry','Kildare','Kilkenny','Laois','Leitrim','Limerick','Longford','Louth','Mayo','Meath','Monaghan','Offaly','Roscommon','Sligo','Tipperary','Tyrone','Waterford','Westmeath','Wexford','Wicklow') NOT NULL,
   phone  int(10) NOT NULL,
   email  varchar(20) NOT NULL,
   payment_method  ENUM ('Visa', 'Amex', 'Cash', 'American Express', 'Mastercard') NOT NULL,
   status  ENUM('Approved','Unapproved'),
   driver_no int(10) NOT NULL,
   PRIMARY KEY (customer_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

支票就像...？

检查driver_no当前吗？

该命令用于查看是否存在某些内容。他们必须有司机号码才能租车。

Answer 1

DROP TABLE IF EXISTS customer;

CREATE TABLE customer
(customer_id SERIAL PRIMARY KEY
,firstname VARCHAR(12) NOT NULL
,licence_no VARCHAR(30) NULL
);

INSERT INTO customer VALUES
(1,'John',NULL),
(2,'Paul','LMW281F'),
(3,'George',NULL),
(4,'Ringo','STAR123');


DROP TABLE IF EXISTS rentals;

CREATE TABLE rentals
(rental_id SERIAL PRIMARY KEY,customer_id INT NOT NULL);

INSERT INTO rentals 
SELECT NULL, customer_id FROM customer WHERE firstname = 'John' AND licence_no IS NOT NULL;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0


SELECT * FROM rentals;
Empty set (0.00 sec)

SQL检查（租车）

1 个答案: