如何根據其他列的值更新列

Question

我有一個如下表

row_wid id code sub_code item_nbr orc_cnt part_cnt variance reporting_date var_start_date
1      1   ABC   PQR     23AB      0       1        1   11-10-2019  NULL
2      1   ABC   PQR     23AB      0       1        1   12-10-2019  NULL
3      1   ABC   PQR     23AB      1       1        0   13-10-2019  NULL
4      1   ABC   PQR     23AB      1       2        1   14-10-2019  NULL
5      1   ABC   PQR     23AB      1       3        2   15-10-2019  NULL

對於 id、code、sub_code 和 item_nbr 的每個組合，我必須使用 min(reporting_date) 更新 var_start_date 列，直到方差字段為零。 方差 = 0 的行應該有 null var_start_date。 之后的下一行應該有下一個分鍾（var_start_date。）。 僅供參考，方差計算為 par_cnt-orc_cnt

所以我的 output 應該是這樣的 -

row_wid id code sub_code item_nbr orc_cnt part_cnt variance reporting_date var_start_date
1      1   ABC   PQR     23AB      0       1        1   11-10-2019  11-10-2019
2      1   ABC   PQR     23AB      0       1        1   12-10-2019  11-10-2019
3      1   ABC   PQR     23AB      1       1        0   13-10-2019  NULL
4      1   ABC   PQR     23AB      1       2        1   14-10-2019  14-10-2019
5      1   ABC   PQR     23AB      1       3        2   15-10-2019  14-10-2019

我正在嘗試使用以下查詢編寫 function 以將數據分成組。

SELECT DISTINCT MIN(reporting_date) 
        OVER (partition by id, code,sub_code,item_nbr ORDER BY row_wid ),
        RANK() OVER (partition by id, code,sub_code,item_nbr ORDER BY row_wid)
        AS rnk,id, code,sub_code,item_nbr,orc_cnt,part_cnt,variance,row_wid
FROM TABLE T1

.但不知道如何包含方差字段來拆分集合。

Answer 1

我會建議：

select t.*,
       (case when variance <> 0
             then min(reporting_date) over (partition by id, code, sub_code, item_nbr, grouping)
        end) as new_reporting_date
from (select t.*,
             sum(case when variance = 0 then 1 else 0 end) over (partition by id, code, sub_code, item_nbr) as grouping
      from t
     ) t;

請注意，這不使用JOIN 。 它應該比答案更有效。

Answer 2

嘗試如下

SELECT T.*, CASE WHEN T.variance = 0 THEN NULL ELSE MIN(reporting_date) OVER (PARTITION BY T1.RANK ORDER BY T1.RANK) END AS New_var_start_date 
FROM mytbl T
LEFT JOIN (
           SELECT row_wid, variance, COUNT(CASE variance WHEN 0 THEN 1 END) OVER (ORDER BY row_wid ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING) +1 AS [Rank]
           FROM mytbl 
          ) T1 ON T.row_wid = T1.row_wid

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