GBase 8c 数据类型——窗口函数

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发表于2023-12-07 15:01:0739次浏览3个评论

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。

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。

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | 8

1 | 3 | 15

1 | 4 | 22

1 | 5 | 29

2 | 5 | 1

2 | 6 | 6

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, Row_number() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, dense_rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | 2

1 | 3 | 3

1 | 4 | 4

1 | 5 | 5

2 | 5 | 1

2 | 6 | 2

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, percent_rank() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | .241379310344828

1 | 3 | .482758620689655

1 | 4 | .724137931034483

1 | 5 | .96551724137931

2 | 5 | 0

2 | 6 | .454545454545455

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, cume_dist() OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | .466666666666667

1 | 3 | .7

1 | 4 | .933333333333333

1 | 5 | 1

2 | 5 | .416666666666667

2 | 6 | 1

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, ntile(3) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | 1

1 | 2 | 2

1 | 3 | 2

1 | 3 | 3

1 | 4 | 3

1 | 5 | 3

2 | 5 | 1

2 | 5 | 2

2 | 6 | 2

2 | 6 | 3

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, lag(d_moy,3,null) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | 1

1 | 3 | 1

1 | 4 | 1

1 | 5 | 1

2 | 5 |

2 | 5 | 2

2 | 6 | 2

(42 rows)

l 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：

gbase=# 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 public.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 | 2

1 | 2 | 2

1 | 2 | 3

1 | 3 | 3

1 | 3 | 4

1 | 4 | 4

1 | 4 | 5

1 | 5 |

2 | 5 | 5

2 | 5 | 6

2 | 6 | 6

2 | 6 |

(42 rows)

l 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：

gbase=# 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 public.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 | 2 | 1

1 | 3 | 1

1 | 4 | 1

1 | 5 | 1

2 | 5 | 5

2 | 6 | 5

(42 rows)

l 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：

gbase=# SELECT d_moy, d_fy_week_seq, last_value(d_moy) OVER(PARTITION BY d_moy ORDER BY d_fy_week_seq) FROM public.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 | 2 | 1

1 | 3 | 1

1 | 4 | 1

1 | 5 | 1

2 | 5 | 2

(35 rows)

l 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：

gbase=# 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 public.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 | 2 | 1

1 | 3 | 1

1 | 4 | 1

1 | 5 | 1

2 | 5 |

(35 rows)

GBase 8c 数据类型——窗口函数

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