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  • 分析函数总结

    转载http://duqiangatom.blog.163.com/blog/static/11502518201051083013421/

    1、rank() over()、dense_rank() over()、row_number() over()

    --排名有重复时,跳过一个,如若有2个第二名,则直接到4,无排名为3的 

     SELECT site_id, SUM(sale_lottery_cnt),rank() over(ORDER BY SUM(sale_lottery_cnt) DESC)
      FROM test

     WHERE report_date = trunc(SYSDATE - 14)
     GROUP BY site_id;

    --排名有重复时,如若有2个第二名,下一个还是排名为3,不跳跃,排名连续
    SELECT site_id, SUM(sale_lottery_cnt),dense_rank() over(ORDER BY SUM(sale_lottery_cnt) DESC)

      FROM test
     WHERE report_date = trunc(SYSDATE - 14)
     GROUP BY site_id;
     
     --排名不可能有重复,即使相同,也会是不同的名次
     SELECT site_id, SUM(sale_lottery_cnt),Row_number() over(ORDER BY SUM(sale_lottery_cnt) DESC)

      FROM test WHERE report_date = trunc(SYSDATE - 14)
     GROUP BY site_id;

     应用1:删除重复记录

     CREATE TABLE test1 AS
             SELECT tt.object_id, tt.object_name FROM user_objects;

     INSERT INTO test1
      SELECT tt.object_id, tt.object_name FROM user_objects tt; --n条记录
     SELECT COUNT(*) FROM user_objects; --2n条
     DELETE FROM test1
     WHERE ROWID IN(SELECT row_id FROM (SELECT ROWID AS row_id,
                            row_number() over(PARTITION BY tt.object_id, tt.object_name ORDER BY ROWID) AS rnn
                       FROM test1 tt) rn  WHERE rn.rnn <>1);--剩下n条记录

    更快的一种方法,用关联delete

    delete  from  test1 t where  t.rowid> (select min(rowid) from test1 d where t.rowid=d.rowid); 

    2、lag(.column, offset) +lead(column ,offset)  over(partition by c1 order by c2) offset default is 1

    ddl test

    create table TEST2
    (
      SITE_ID          NUMBER not null,
      SALE_LOTTERY_CNT NUMBER
    );

     insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (132623, 10);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (633423, 4);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (132523, 2);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (183523, 2);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (183524, 4);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (183524, 19);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (183623, 4);

    insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
    values (132623, 19);

    SELECT site_id, sale_lottery_cnt,
           lag(sale_lottery_cnt, 1) over(PARTITION BY site_id ORDER BY sale_lottery_cnt DESC NULLS FIRST) AS "分组排序后取前一个记录字段值",
           lead(sale_lottery_cnt, 1) over(PARTITION BY site_id ORDER BY sale_lottery_cnt DESC NULLS FIRST) AS "分组排序后取后一个记录字段值"
      FROM test
     WHERE report_date = trunc(SYSDATE - 14);

    3、min(c1)/max/avg/sum over(partition by c2) 返回分组中的聚合值,但是行数不变,不像聚合函数行数变少

    SELECT site_id, sale_lottery_cnt, MAX(sale_lottery_cnt) over(PARTITION BY site_id),
           MIN(sale_lottery_cnt) over(PARTITION BY site_id),
           AVG(sale_lottery_cnt) over(PARTITION BY site_id),
           SUM(sale_lottery_cnt) over(PARTITION BY site_id)
      FROM test2
     ORDER BY 1;--行数无变化,前后行数相等

    SELECT site_id, MAX(sale_lottery_cnt), SUM(sale_lottery_cnt), AVG(sale_lottery_cnt),
           MIN(sale_lottery_cnt)
      FROM test2
     GROUP BY site_id;--返回聚合完的行数,与分组数相同

    4、aggregate function(列) keep (dense_rank  first  [last] order by c2 desc)   over(partition by c1 ) )

      SELECT site_id, sale_lottery_cnt,
            --先按分组排序,然后取第一个或者最后一个,但是也有可能第一个或者最后一个有多于1条记录,此时,前面的max聚合函数就起作用了
           MAX(sale_lottery_cnt) keep(dense_rank LAST ORDER (BY sale_lottery_cnt DESC) over(PARTITION BY site_id),
           MIN(sale_lottery_cnt) keep(dense_rank LAST ORDER BY sale_lottery_cnt DESC) over(PARTITION BY site_id)
      FROM test2;

    5、RATIO_TO_REPORT (column) over()计算 column/sum(column)

            SELECT ID,SORT,color,ratio_to_report(NUM) OVER()  FROM TEST;

     1 book       red        0.2
    1 book       blue       0.133333333333333
    1 book       green      0.133333333333333
    1 book       red        0.133333333333333
    1 car        blue       0.133333333333333
    1 car        red        0.133333333333333
    2 car        red        0.133333333333333

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  • 原文地址:https://www.cnblogs.com/future2012lg/p/2883197.html
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