● 设有商品关系P(商品名,条形码,供应商号,价格,数量), “条形码”唯一标识关系P中的每一个元组,商品名不能为空,供应商号是关系P的外键。另有供应商关系S(供应商号,供应商名,地址,电话)。关系 P 中的商品名是唯一的。建立商品关系 P 的 SQL
语句如下所示:
CREATE TABLE P( 商品名CHAR(30) (57) ,
条形码CHAR(30) (58) ,
供应商号 CHAR(5) ,
价格 CHAR(20) ,
数量CHAR(20)
(59) (供应商号) REFERENCES S(供应商号));
(57)
● The (74) scheme in a database system is responsible for the detection of failures and for the restoration of the database to a state that existed before the occurrence of the failure.
(74)
● Software (75) focuses on three attributes of the program: software architecture, data structure, and procedural detail.
(75)
● (73) statement can perform. a calculation and store the result in a variable so that it can be used later.
(73)
● (71) means that a program written for one computer system can be compiled and run on another system with little or no modification.
(71)
● Data items are added or deleted from the list only at the top of the (72) .
(72)
● 在http://www.test.com/main/index.htm中,index.htm是 (69) 。
(69)
● POP3服务默认的TCP 端口号是 (70) 。
(70)
● HTML语言中,可使用 (67) 标签将脚本插入HTML 文档。
(67)