create table – sql 命令示例

下面的示例创建了一个新的数据库 mydata1。用 create table 创建了两个表salesman 和 customer，它们自动添加到数据库中。第二个 create table 命令中的foreign key 和 reference 子句创建了 salesman 和 customer 表间的一个永久的一对多关系，然后用 modify database 来显示两表间的关系。第三个 defaultclauses in the third create table 命令中的 default 子句用于建立默认值，check 和 error 子句为输入特定字段内容建立商务规则。使用 modifydatabase 命令显示三个表的关系。

close databases
clear
* create mydata database in the current directory or folder
create database mydata1
* create a salesman table with a primary key
create table salesman ;
   (salesid c(6) primary key, ;
   salename c(20))
* create a customer table and relate it to the salesman table.
create table customer ;
   (salesid c(6), ;
   custid i primary key, ;
   custname c(20) unique,   ;
   salesbranch c(3), ;
   foreign key salesid tag salesid references salesman)
* create an orders table related to customer with its own primary
* key and some business rules such as defaults & checks.
create table orders ;
   (orderid i primary key, ;
      custid i references customer tag custid, ;
      orderamt y(4), ;
      orderqty i ;
      default 10 ;
      check (orderqty > 9) ;
      error "order quantity must be at least 10", ;
         discpercent n(6,2) null ;
      default .null., ;
      check (orderamt > 0) error "order amount must be > 0" )
* display new database, tables, and relationships
modify database
* delete example files
set safety off && to suppress verification message
close databases     && close database before deleting
delete database mydata1 deletetables