窗口函数是一种分析型的OLAP函数,OLAP是online analytical processing的简称,意思是对数据库数据进行实时分析处理。


列存表目前只支持rank(expression)和row_number(expression)两个函数。

窗口函数与OVER语句一起使用。OVER语句用于对数据进行分组,并对组内元素进行排序。窗口函数用于给组内的值生成序号。

说明:窗口函数中的order by后面必须跟字段名,若order by后面跟数字,该数字会被按照常量处理,因此对目标列没有起到排序的作用。

  • RANK()
    描述:RANK函数为各组内值生成跳跃排序序号,其中,相同的值具有相同序号。
    返回值类型:BIGINT
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | rank
-------+---------------+------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 8
1 | 2 | 8
1 | 2 | 8
1 | 2 | 8
1 | 2 | 8
1 | 2 | 8
1 | 2 | 8
1 | 3 | 15
1 | 3 | 15
1 | 3 | 15
1 | 3 | 15
1 | 3 | 15
1 | 3 | 15
1 | 3 | 15
1 | 4 | 22
1 | 4 | 22
1 | 4 | 22
1 | 4 | 22
1 | 4 | 22
1 | 4 | 22
1 | 4 | 22
1 | 5 | 29
1 | 5 | 29
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
(42 rows)
  • ROW_NUMBER()
    描述:ROW_NUMBER函数为各组内值生成连续排序序号,其中,相同的值其序号也不相同。
    返回值类型:BIGINT
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, Row_number() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim  WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | row_number
-------+---------------+------------
1 | 1 | 1
1 | 1 | 2
1 | 1 | 3
1 | 1 | 4
1 | 1 | 5
1 | 1 | 6
1 | 1 | 7
1 | 2 | 8
1 | 2 | 9
1 | 2 | 10
1 | 2 | 11
1 | 2 | 12
1 | 2 | 13
1 | 2 | 14
1 | 3 | 15
1 | 3 | 16
1 | 3 | 17
1 | 3 | 18
1 | 3 | 19
1 | 3 | 20
1 | 3 | 21
1 | 4 | 22
1 | 4 | 23
1 | 4 | 24
1 | 4 | 25
1 | 4 | 26
1 | 4 | 27
1 | 4 | 28
1 | 5 | 29
1 | 5 | 30
2 | 5 | 1
2 | 5 | 2
2 | 5 | 3
2 | 5 | 4
2 | 5 | 5
2 | 6 | 6
2 | 6 | 7
2 | 6 | 8
2 | 6 | 9
2 | 6 | 10
2 | 6 | 11
2 | 6 | 12
(42 rows)
  • DENSE_RANK()
    描述:DENSE_RANK函数为各组内值生成连续排序序号,其中,相同的值具有相同序号。
    返回值类型:BIGINT
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, dense_rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | dense_rank
-------+---------------+------------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 5 | 5
1 | 5 | 5
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
(42 rows)
  • PERCENT_RANK()
    描述:PERCENT_RANK函数为各组内对应值生成相对序号,即根据公式 (rank - 1) / (total rows - 1)计算所得的值。其中rank为该值依据RANK函数所生成的对应序号,totalrows为该分组内的总元素个数。
    返回值类型:DOUBLE PRECISION
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, percent_rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | percent_rank
-------+---------------+------------------
1 | 1 | 0
1 | 1 | 0
1 | 1 | 0
1 | 1 | 0
1 | 1 | 0
1 | 1 | 0
1 | 1 | 0
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 2 | .241379310344828
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 3 | .482758620689655
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 4 | .724137931034483
1 | 5 | .96551724137931
1 | 5 | .96551724137931
2 | 5 | 0
2 | 5 | 0
2 | 5 | 0
2 | 5 | 0
2 | 5 | 0
2 | 6 | .454545454545455
2 | 6 | .454545454545455
2 | 6 | .454545454545455
2 | 6 | .454545454545455
2 | 6 | .454545454545455
2 | 6 | .454545454545455
2 | 6 | .454545454545455
(42 rows)
  • CUME_DIST()
    描述:CUME_DIST函数为各组内对应值生成累积分布序号。即根据公式(小于等于当前值的数据行数)/(该分组总行数totalrows)计算所得的相对序号。
    返回值类型:DOUBLE PRECISION
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, cume_dist() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim e_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | cume_dist
-------+---------------+------------------
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 1 | .233333333333333
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 2 | .466666666666667
1 | 3 | .7
1 | 3 | .7
1 | 3 | .7
1 | 3 | .7
1 | 3 | .7
1 | 3 | .7
1 | 3 | .7
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 4 | .933333333333333
1 | 5 | 1
1 | 5 | 1
2 | 5 | .416666666666667
2 | 5 | .416666666666667
2 | 5 | .416666666666667
2 | 5 | .416666666666667
2 | 5 | .416666666666667
2 | 6 | 1
2 | 6 | 1
2 | 6 | 1
2 | 6 | 1
2 | 6 | 1
2 | 6 | 1
2 | 6 | 1
(42 rows)
  • NTILE(num_buckets integer)
    描述:NTILE函数根据num_buckets integer将有序的数据集合平均分配到num_buckets所指定数量的桶中,并将桶号分配给每一行。分配时应尽量做到平均分配。
    返回值类型:INTEGER
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, ntile(3) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | ntile
-------+---------------+-------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 3 | 2
1 | 3 | 2
1 | 3 | 2
1 | 3 | 2
1 | 3 | 2
1 | 3 | 2
1 | 3 | 3
1 | 4 | 3
1 | 4 | 3
1 | 4 | 3
1 | 4 | 3
1 | 4 | 3
1 | 4 | 3
1 | 4 | 3
1 | 5 | 3
1 | 5 | 3
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 1
2 | 5 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 3
2 | 6 | 3
2 | 6 | 3
2 | 6 | 3
(42 rows)
  • LAG(value any [, offset integer [, default any ]])
    描述:LAG函数为各组内对应值生成滞后值。即当前值对应的行数往前偏移offset位后所得行的value值作为序号。若经过偏移后行数不存在,则对应结果取为default值。若无指定,在默认情况下,offset取为1,default值取为NULL。
    返回值类型:与参数数据类型相同。
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, lag(d_moy,3,null) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | lag
-------+---------------+-----
1 | 1 |
1 | 1 |
1 | 1 |
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 5 | 1
1 | 5 | 1
2 | 5 |
2 | 5 |
2 | 5 |
2 | 5 | 2
2 | 5 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
2 | 6 | 2
(42 rows)
  • LEAD(value any [, offset integer [, default any ]])
    描述:LEAD函数为各组内对应值生成提前值。即当前值对应的行数向后偏移offset位后所得行的value值作为序号。若经过向后偏移后行数超过当前组内的总行数,则对应结果取为default值。若无指定,在默认情况下,offset取为1,default值取为NULL。
    返回值类型:与参数数据类型相同。
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, lead(d_fy_week_seq,2) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM  tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2;
d_moy | d_fy_week_seq | lead
-------+---------------+------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 2
1 | 1 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 2
1 | 2 | 3
1 | 2 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 3
1 | 3 | 4
1 | 3 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 4
1 | 4 | 5
1 | 4 | 5
1 | 5 |
1 | 5 |
2 | 5 | 5
2 | 5 | 5
2 | 5 | 5
2 | 5 | 6
2 | 5 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 | 6
2 | 6 |
2 | 6 |
(42 rows)
  • FIRST_VALUE(value any)
    描述:FIRST_VALUE函数取各组内的第一个值作为返回结果。
    返回值类型:与参数数据类型相同。
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, first_value(d_fy_week_seq) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 7 ORDER BY 1,2; 
d_moy | d_fy_week_seq | first_value
-------+---------------+-------------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 5 | 1
1 | 5 | 1
2 | 5 | 5
2 | 5 | 5
2 | 5 | 5
2 | 5 | 5
2 | 5 | 5
2 | 6 | 5
2 | 6 | 5
2 | 6 | 5
2 | 6 | 5
2 | 6 | 5
2 | 6 | 5
2 | 6 | 5
(42 rows)
  • LAST_VALUE(value any)
    描述:LAST_VALUE函数取各组内的最后一个值作为返回结果。
    返回值类型:与参数数据类型相同。
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, last_value(d_moy) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 6 ORDER BY 1,2;
d_moy | d_fy_week_seq | last_value
-------+---------------+------------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 5 | 1
1 | 5 | 1
2 | 5 | 2
2 | 5 | 2
2 | 5 | 2
2 | 5 | 2
2 | 5 | 2
(35 rows)
  • NTH_VALUE(value any, nth integer)
    描述:NTH_VALUE函数返回该组内的第nth行作为结果。若该行不存在,则默认返回NULL。
    返回值类型:与参数数据类型相同。
    示例:
openGauss=# SELECT d_moy, d_fy_week_seq, nth_value(d_fy_week_seq,6) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM tpcds.date_dim WHERE d_moy < 4 AND d_fy_week_seq < 6 ORDER BY 1,2;
d_moy | d_fy_week_seq | nth_value
-------+---------------+-----------
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 1 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 2 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 3 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 4 | 1
1 | 5 | 1
1 | 5 | 1
2 | 5 |
2 | 5 |
2 | 5 |
2 | 5 |
2 | 5 |
(35 rows)