SQL CASE 表达式分组“问题”

Question

I'm trying to get some data out of a table and look at if a record exists in 1 year chunks.

The main table looks like this

VM_HI_MAGIC	VM_HI_DATEOUT	VM_HI_HEVTYPE	VM_HI_VEHICLE	VM_HI_CODE_001
336338	2014-07-07	SER	116591	VHC
336493	2014-07-07	SER	116591	S01
336502	2014-07-07	SER	116591	S01
547889	2015-05-11	SER	116591	MOT
547891	2015-05-11	SER	116591	VHC
585385	2015-07-02	SER	116591	VHC
585509	2015-07-02	SER	116591	S01
585571	2015-07-02	SER	116591	S01
1313	NULL	SER	116591	MEC
92364	2013-07-03	SER	116591	S01
92365	2013-07-03	SER	116591	VHC

The code the generate this was

SELECT VM_HI_MAGIC
      ,VM_HI_DATEOUT
      ,VM_HI_HEVTYPE
      ,VM_HI_VEHICLE
      ,VM_HI_CODE_001

FROM VM_00_HISTORY

WHERE VM_HI_HEVTYPE = 'SER' AND VM_HI_VEHICLE = 116591

So far, I've achieved the following

VM_HI_VEHICLE	-7	-6	-5	-4	-3	-2	-1
116591	0	0	0	0	0	0	0
116591	0	1	0	0	0	0	0
116591	1	0	0	0	0	0	0

I got to this using the following code

SELECT DISTINCT
    VM_HI_VEHICLE
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -7, GETDATE()) AND DATEADD(year, -6, GETDATE()) THEN 1
        ELSE 0
    END AS '-7'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -6, GETDATE()) AND DATEADD(year, -5, GETDATE()) THEN 1
        ELSE 0
    END AS '-6'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -5, GETDATE()) AND DATEADD(year, -4, GETDATE()) THEN 1
        ELSE 0
    END AS '-5'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -4, GETDATE()) AND DATEADD(year, -3, GETDATE()) THEN 1
        ELSE 0
    END AS '-4'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -3, GETDATE()) AND DATEADD(year, -2, GETDATE()) THEN 1
        ELSE 0
    END AS '-3'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -2, GETDATE()) AND DATEADD(year, -1, GETDATE()) THEN 1
        ELSE 0
    END AS '-2'
    ,CASE
        WHEN VM_HI_DATEOUT between DATEADD(year, -1, GETDATE()) AND GETDATE() THEN 1
        ELSE 0
    END AS '-1'
  FROM VM_00_HISTORY

  WHERE VM_HI_VEHICLE = 116591  AND VM_HI_HEVTYPE = 'SER' AND VM_HI_CODE_001 LIKE 'S01'

My desired output is

VM_HI_VEHICLE	-7	-6	-5	-4	-3	-2	-1
116591	1	1	0	0	0	0	0

I can then remove VM_HI_VEHICLE from the WHERE clause to display a list of all cars we're seen within the past 7 years to look at retention.

I have attempted adding GROUP BY VM_HI_VEHICLE but this needs VM_HI_DATEOUT to be included as well due to it being in the CASE expression, which leaves with the same result.

How can I group all 3 output records together to give the desired output?

Thank you for reading.

Answer 1

You seem to want aggregation:

SELECT VM_HI_VEHICLE,
       MAX(CASE WHEN VM_HI_DATEOUT between DATEADD(year, -7, GETDATE()) AND DATEADD(year, -6, GETDATE()) THEN 1
                ELSE 0
            END) AS [-7],
       MAX(CASE WHEN VM_HI_DATEOUT between DATEADD(year, -6, GETDATE()) AND DATEADD(year, -5, GETDATE()) THEN 1
                ELSE 0
          END) AS [-6],
       . . .
FROM VM_00_HISTORY
WHERE VM_HI_VEHICLE = 116591 AND VM_HI_HEVTYPE = 'SER' AND VM_HI_CODE_001 LIKE 'S01'
GROUP BY VM_HI_VEHICLE;

Note: I strongly discourage you from using single quotes for column aliases. This just causes confusion and hard-to-debug errors.

Answer 2

Sounds like you should be grouping by the vehicle then the year (use the year() function to get the year) then using the count() function on any other column to see how many records appear then present it as a pivot table if you must have the output formatted the way you have it formatted.