開窗函式over(partition by .. [order by ..])用法
阿新 • • 發佈：2019-01-26
1、/** 建立表 */
create table test_orer_partition_by
(
prov_name varchar(20),
city_name varchar(50),
val_cnt int
) ;
2、/** 插入測試資料 */
insert into test_orer_partition_by values ('GS', 'LZ', 234) ;
insert into test_orer_partition_by values ('GS', 'BY', 34) ;
insert into test_orer_partition_by values ('GS', 'DX', 4) ;
insert into test_orer_partition_by values ('GS', 'LN', 67) ;
insert into test_orer_partition_by values ('GS', 'GN', 67) ;
insert into test_orer_partition_by values ('GS', 'QY', 67) ;
insert into test_orer_partition_by values ('SX', 'XA', 34) ;
insert into test_orer_partition_by values ('SX', 'YA', 85) ;
insert into test_orer_partition_by values ('SX', 'BJ', 254) ;
insert into test_orer_partition_by values ('SX', 'HZ', 99) ;
insert into test_orer_partition_by values ('SX', 'XY', 100) ;
insert into test_orer_partition_by values ('SX', 'SL', 23) ;
3、排序（row_number、rank、dense_rank） 
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 rst from test_orer_partition_by ;
4、聚合函式（sum、avg、count、max、min、first_value、last_value） /** sum() over([partition by prov_name [ORDER BY val_cnt]]) */ 
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 ;
vg、count、max、min、first_value、last_value與sum用法一模一樣，不在贅述。 5、分許函式（lag、lead） /** lead() over([partition by prov_name [ORDER BY val_cnt]]) */ lag、lead有三個引數，第一個是表示式或欄位，第二個是偏移量，第三個是為控制賦值 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 ;
lag與lead用法相同，只是偏移順序相反。
from test_orer_partition_by ;
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 rst from test_orer_partition_by ;
4、聚合函式（sum、avg、count、max、min、first_value、last_value） /** sum() over([partition by prov_name [ORDER BY val_cnt]]) */
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 ;
vg、count、max、min、first_value、last_value與sum用法一模一樣，不在贅述。 5、分許函式（lag、lead） /** lead() over([partition by prov_name [ORDER BY val_cnt]]) */ lag、lead有三個引數，第一個是表示式或欄位，第二個是偏移量，第三個是為控制賦值 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 ;
lag與lead用法相同，只是偏移順序相反。