开窗函数_3

create table test_orer_partition_by
(
    prov_name varchar(20),
    city_name varchar(50),
    val_cnt int
) ;
2、/** 插入测试数据 */
insert into test_orer_partition_by values (‘GS‘, ‘LZ‘, 234) ,
     (‘GS‘, ‘BY‘, 34) ,
     (‘GS‘, ‘DX‘, 4) ,
    (‘GS‘, ‘LN‘, 67) ,
     (‘GS‘, ‘GN‘, 67) ,
    (‘GS‘, ‘QY‘, 67) ,
     (‘SX‘, ‘XA‘, 34) ,
     (‘SX‘, ‘YA‘, 85) ,
    (‘SX‘, ‘BJ‘, 254) ,
    (‘SX‘, ‘HZ‘, 99) ,
     (‘SX‘, ‘XY‘, 100),
    (‘SX‘, ‘SL‘, 23) ;

SELECT * FROM test_orer_partition_by

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3、排序（row_number()、rank()、dense_rank(),NTILE(n)  ）
3.1 /** row_number() over(partition by prov_name ORDER BY val_cnt) */
SELECT prov_name,city_name,val_cnt,
              row_number() over(order by val_cnt) as RowID                ------>未分区，排序

FROM test_orer_partition_by
-----------------------------------------------
SELECT prov_name,city_name,val_cnt,
              row_number() over(partition by prov_name order by val_cnt ) as RowID    ------>先分区，排序

FROM test_orer_partition_by
----------------------------------------------
3.2 /** rank() over(partition by prov_name ORDER BY val_cnt) */
SELECT prov_name,city_name,val_cnt,
              rank() over(partition by prov_name order by val_cnt ) as RankID

FROM test_orer_partition_by
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3.3 /** dense_rank() over(partition by prov_name ORDER BY val_cnt) */
select prov_name, city_name, val_cnt,
dense_rank() over(partition by prov_name ORDER BY val_cnt) AS Dense_RankID
from test_orer_partition_by ;
----------------------------------------------
3.4 /** NTILE() over(partition by prov_name ORDER BY val_cnt) */
select prov_name, city_name, val_cnt,
NTILE(5) over(partition by prov_name ORDER BY val_cnt) AS NTILEID
from test_orer_partition_by ;

-----------------------------------------------
select prov_name, city_name, val_cnt,
NTILE(5) over(ORDER BY val_cnt) AS NTILEID
from test_orer_partition_by ;
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4、聚合函数（sum、avg、count、max、min、first_value、last_value）
/** sum() over([partition by prov_name [ORDER BY val_cnt]]) */
有order by；按照排序连续累加；
无order by，计算partition by后的和；
over()中没有partition by，计算所有数据总和
select prov_name, city_name, val_cnt,
         sum(val_cnt) over(partition by prov_name ORDER BY val_cnt) AS rst
from test_orer_partition_by ;
----------------------------------------------
select prov_name, city_name, val_cnt,
sum(val_cnt) over(partition by prov_name) AS rst
from test_orer_partition_by ;
----------------------------------------------
select prov_name, city_name, val_cnt,
sum(val_cnt) over() AS rst
from test_orer_partition_by ;
----------------------------------------------
5、分许函数（lag、lead）
/** lead() over([partition by prov_name [ORDER BY val_cnt]]) */
lag、lead有三个参数，第一个是表达式或字段，第二个是偏移量，第三个是为控制赋值
select prov_name, city_name, val_cnt,
lead(val_cnt, 1) over(partition BY prov_name ORDER BY val_cnt) AS rst
from test_orer_partition_by ;
----------------------------------------------
select prov_name, city_name, val_cnt,
    lead(val_cnt, 2) over(partition BY prov_name ORDER BY val_cnt) AS rst
from test_orer_partition_by ;
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