SQL查询空值基于另一个替换

Question

因此，我使用ROW_NUMBER（）OVER（PARTITION BY）查询返回数据和行号，并将其放入临时表中。初始输出显示屏幕截图：

。

在这里，我需要在bt_newlabel列中分别替换为null。因此，行号1-4正在进行中，行号5-9将被承保，行号10-13将被执行，依此类推。

我碰壁试图确定该如何做。感谢您对我的处理方法的帮助或投入。

Answer 1

一种方法是先分配组，然后分配值。如：

select t.*, max(bt_newlabel) over (partition by grp) as new_newlabel
from (select t.*, count(bt_newlabel) over (order by bt_stamp) as grp
      from t
     ) t;

该组只是先前在数据中看到的已知值的数量。

您可以使用以下方式更新该字段：

with toupdate as (
      select t.*, max(bt_newlabel) over (partition by grp) as new_newlabel
      from (select t.*, count(bt_newlabel) over (order by bt_stamp) as grp
            from t
           ) t
     )
update toupdate
    set bt_newlabel = new_newlabel
    where bt_newlabel is null;

Answer 2

如果我了解您要执行的操作，则这是您需要在临时表上执行的更新类型：

--This will update rows 1-4 to 'Pre-Underwritting'

UPDATE temp_table SET bt_newlabel = 'Pre-Underwritting'
WHERE rownumber between 
1 AND (SELECT TOP 1 rownumber FROM temp_table WHERE bt_oldlabel = 'Pre-Underwritting');

--This will update rows 5-9 to 'Underwritting'

UPDATE temp_table SET bt_newlabel = 'Underwritting'
WHERE rownumber between 
(SELECT TOP 1 rownumber FROM temp_table WHERE bt_oldlabel = 'Pre-Underwritting')
AND
(SELECT TOP 1 rownumber FROM temp_table WHERE bt_oldlabel = 'Underwritting');

--This will update rows 10-13 to 'Implementation'

UPDATE temp_table SET bt_newlabel = 'Implementation'
WHERE rownumber between 
(SELECT TOP 1 rownumber FROM temp_table WHERE bt_oldlabel = 'Underwritting')
AND
(SELECT TOP 1 rownumber FROM temp_table WHERE bt_oldlabel = 'Implementation');

我制作了一个有效的小提琴以检查结果：http://sqlfiddle.com/#!18/1cae2/1/3