16、U-SQL：功能、执行流程与扩展方法详解

U-SQL：功能、执行流程与扩展方法详解

1. U-SQL 基础代码示例

下面是一段 U-SQL 代码示例，展示了如何进行数据提取、连接、聚合等操作：

REFERENCE MyDB.MyAssembly <2>
CREATE TABLE T <2> (cid <2> int <3>, first_order DateTime, last_order DateTime, order_count 
int, order_amount float);
@o = EXTRACT oid int, cid int, odate DateTime, amount float <3>
    FROM <3> "/input/orders.txt" <1>
    USING Extractors.Csv();<3>
@c = EXTRACT cid int, name string, city string <3>
    FROM <3> "/input/customers.txt" <1>
    USING Extractors.Csv(); <3>
@j = SELECT <3> c.cid,
        MIN <3> (o.date) AS firstorder,
        MAX <3> (o.date) as lastorder,
        COUNT <3> (o.oid) AS ordercnt,
        AGG<My