Clickhouse 開窗函數

向大神學習：https://mp.weixin.qq.com/s/ubahKb5NajqHv0LGvAP-iw

SELECT arrayEnumerate([10,20,30,10,40]) AS row_number, /*按照數據順序輸出應的ID*/
       arrayEnumerateDense([10,20,30,10,40]) AS dense_rank, /*按照數據出現輸出ID,其中數字相同的，ID 也會相同*/
       arrayEnumerateUniq([10,20,30,10,40]) AS uniq_ran ; /*輸出數據出現次數*/



CREATE TABLE test_data engine = Memory AS
WITH(
  SELECT ['A','A','A','A','B','B','B','B','B','A','59','90','80','80','65','75','78','88','99','70']
)AS dict;
select * from test_data ;

/*第一步：按val 排序，因為條件是 order by val,按照分時升序排列*/
SELECT * FROM test_data ORDER BY val;


/*第二步：按id 分組，因為條件是PARTITION BY id*/
select id
from
(
     select * from test_data order by val as asc
    )
group by id ;

/*第三步，計算val的RANK ，需要用到剛介紹的幾個
  arrayEnumerate*函數，由於它們的入參要求數組，
  所以先使用groupArray將val轉成數組：*/
select
    id,
       groupArray(val) as arr_val,
       arrayEnumerate(arr_val) as row_number,
       arrayEnumerateDense(arr_val) as dense_rank,
       arrayEnumerateUniq(arr_val) as uniq_rank
from
(
select *
from test_data
order by val asc
    ) group by id;

/*第四步：數組展開，利用ARRAY JOIN 將數組展開，並按照id,RANK 列排序*/
select
id,
       val,
       row_number,
       dense_rank,
       uniq_rank
from
(
select
id,
       groupArray(val) as arr_val,
       arrayEnumerate(arr_val) as row_number,
       arrayEnumerateDense(arr_val) as dense_rank,
       arrayEnumerateUniq(arr_val) as uniq_rank
from
     (
select * from test_data
order by val asc
    )
group by id
    )
ARRAY JOIN
arr_val as val,
row_number,
dense_rank,
uniq_rank
order by
id asc,
         row_number asc,
         dense_rank asc