oracle 隨機數及相應函數

        先貼一段sql:

SELECT   *
      FROM   check_for_busi_result SAMPLE BLOCK (10) SEED (11)
     WHERE   ROWNUM <= 5;
     /*   1.sample只對單表生效，不能用於錶鏈接、遠程表、視圖
          2.sample會使SQL自動使用CBO                     */
     
     /* sample  按記錄採樣   seed(3) 返回固定的結果集 */
      select count(*) from check_for_busi_result sample(18);
      
       SELECT   *
      FROM   check_for_busi_result SAMPLE (18)
     WHERE   ROWNUM <= 5;
     
     /* SAMPLE BLOCK (18) 按數據塊採樣  「採樣表掃描」隨機抽取10%的記錄，再從中隨機查詢5條記錄 */
     select count(*) from check_for_busi_result sample block(18) ;
     
         SELECT   *
      FROM   check_for_busi_result SAMPLE BLOCK (18) 
     WHERE   ROWNUM <= 5;
     /*  獲取一個隨機數
    --（0-10的整數） */
     SELECT   TRUNC (DBMS_RANDOM.VALUE (0, 10)) randomNum FROM DUAL;
     
     取表隨機數據
      SELECT   *
      FROM   (  SELECT   *
                  FROM   check_for_busi_result  
              ORDER BY   DBMS_RANDOM.VALUE)
     WHERE   ROWNUM <= 3
     
      SELECT   *
      FROM   (  SELECT   *
                  FROM   check_for_busi_result
               
              ORDER BY   DBMS_RANDOM.VALUE(1,3))
     WHERE   ROWNUM <= 3
     
     SELECT   *
      FROM   (  SELECT   *
                  FROM   check_for_busi_result
                
              ORDER BY   DBMS_RANDOM.random)
     WHERE   ROWNUM <= 3
     
     
      SELECT   *
      FROM   (  SELECT   *
                  FROM   check_for_busi_result
                
              ORDER BY   sys_guid())
     WHERE   ROWNUM <= 3

 

貼個資源博客：https://blog.csdn.net/bbliutao/article/details/7727322；