SQL server create 如何根据前一行条件创建新列

Question

我正在尝试创建一个新列，其值取决于之前的索引行值，如下例所示：

Index	ID	AGE	SEX	HireMonth	Tag
1	101	23	M	9	101
2	102	32	M	12	102
3	103	25	F	11	1
4	104	29	M	10	104
5	105	45	F	1	1
6	106	21	M	7	106
7	107	56	F	6	107
8	108	12	M	4	108

以下是我创建 Tag 列的方法：

CASE WHEN AGE > 25 AND HireMonth => 9 
     THEN (next row value = 1 AND same row ID ) 
     ELSE ID
END AS Tag

Answer 1

你试过了吗：

select [Index], ID, AGE, SEX, HireMonth, 
       CASE WHEN LAG(AGE, 1) OVER (ORDER BY [Index]) > 25 AND LAG(HireMonth, 1) OVER (ORDER BY [Index]) >= 9 
           THEN 1 
           ELSE ID 
           END AS Tag
FROM SOME_TABLE

Answer 2

您可以使用 SELF LEFT JOIN 将每个 ID 与其前一个 ID 相匹配。如果您指出的要求匹配，那么您可以分配 1 否则您分配同一行的 ID，使用 CASE 语句。

SELECT 
    t1.*,
    CASE WHEN t2.ID_ IS NOT NULL THEN 1 ELSE t1.ID_ END AS Tag
FROM      tab t1 
LEFT JOIN tab t2
       ON t1.ID_ = t2.ID_ +1
      AND t2.AGE > 25
      AND t2.HireMonth > 8

试试看 here.

SQL server create 如何根据前一行条件创建新列

SQL server create how to create a new column based on previous row condition

sql

sql-server

Index	ID	AGE	SEX	HireMonth	Tag
1	101	23	M	9	101
2	102	32	M	12	102
3	103	25	F	11	1
4	104	29	M	10	104
5	105	45	F	1	1
6	106	21	M	7	106
7	107	56	F	6	107
8	108	12	M	4	108

Index	ID	AGE	SEX	HireMonth	Tag
1	101	23	M	9	101
2	102	32	M	12	102
3	103	25	F	11	1
4	104	29	M	10	104
5	105	45	F	1	1
6	106	21	M	7	106
7	107	56	F	6	107
8	108	12	M	4	108

Index	ID	AGE	SEX	HireMonth	Tag
1	101	23	M	9	101
2	102	32	M	12	102
3	103	25	F	11	1
4	104	29	M	10	104
5	105	45	F	1	1
6	106	21	M	7	106
7	107	56	F	6	107
8	108	12	M	4	108