Case语句中的聚合函数

Question

I am having some trouble with aggregate functions inside a case statement. I want to write a query that will set field A to N if it is equal to the minimum date of field A, or M otherwise.

Sample Code:

SELECT *, CASE
       WHEN Field_A = MIN(FIELD_A) THEN 'JN'
       ELSE 'JP'
       END AS JUDI

FROM TABLE_1
GROUP BY *

I am not sure why the command runs but does not execute correctly. It labels all rows as JN in the JUDI Field. How can I fix this?

I am running SQL Server 7. What I want to achieve is that in a list of rows with different dates it labels those with the earliest date with JN and subsequent dates with JP .

Answer 1

Use window functions:

SELECT t.*,
       (CASE WHEN t.Field_A = MIN(t.FIELD_A) OVER () THEN 'JN'
             ELSE 'JP'
        END) AS JUDI
FROM TABLE_1 t;

You don't need aggregation over the entire table for this.