示例：创建受限警报

创建受限警报应用程序

1. 创建一个 Kinesis Data Analytics 应用程序，如 Kinesis Data Analytics 入门练习中所述。

2. 在 Kinesis Data Analytics 上的 SQL 编辑器中，将应用程序代码替换为以下内容：

   CREATE OR REPLACE STREAM "CHANGE_STREAM" 
              (ticker_symbol VARCHAR(4), 
               sector        VARCHAR(12), 
               change        DOUBLE, 
               price         DOUBLE);
   
   CREATE OR REPLACE PUMP "change_pump" AS 
      INSERT INTO "CHANGE_STREAM"
         SELECT STREAM ticker_symbol, sector, change, price 
         FROM   "SOURCE_SQL_STREAM_001"
         WHERE  (ABS(Change / (Price - Change)) * 100) > 1;
         
   -- ** Trigger Count and Limit **
   -- Counts "triggers" or those values that evaluated true against the previous where clause
   -- Then provides its own limit on the number of triggers per hour per ticker symbol to what
   -- is specified in the WHERE clause
   
   CREATE OR REPLACE STREAM TRIGGER_COUNT_STREAM (
      ticker_symbol VARCHAR(4), 
      change REAL,
      trigger_count INTEGER);
   
   CREATE OR REPLACE PUMP trigger_count_pump AS INSERT INTO TRIGGER_COUNT_STREAM
   SELECT STREAM ticker_symbol, change, trigger_count
   FROM (
       SELECT STREAM ticker_symbol, change, COUNT(*) OVER W1 as trigger_count
       FROM "CHANGE_STREAM"
       --window to perform aggregations over last minute to keep track of triggers
       WINDOW W1 AS (PARTITION BY ticker_symbol RANGE INTERVAL '1' MINUTE PRECEDING)
   )
   WHERE trigger_count >= 1;

   应用程序代码中的 SELECT 语句将在 SOURCE_SQL_STREAM_001 中筛选出显示股票价格更改大于 1% 的行，并使用数据泵将这些行插入另一个应用程序内部流 CHANGE_STREAM。

   然后，应用程序为受限警报创建第二个名为 TRIGGER_COUNT_STREAM 的流。第二个查询从一个窗口中选择记录，每次记录被允许进入该窗口时，该窗口都向前跳，以便每个股票报价每分钟只有一个记录被写入到流中。

3. 选择 保存并运行 SQL。