Order by column which casted to varchar

Question

situation is that, i want to prepare datasets for front end chart. the raw data from table contains

LAC | FLUID_MERIT|FA_BDATE   |GRP |FARM_FK
------------------------------------------
0   |234.56      |2020-01-01 |12  |10048
1   |234.56      |2009-01-01 |13  |10048
10  |234.56      |2020-01-01 |13  |10048
0   |234.56      |2020-01-01 |13  |10049
2   |234.56      |2009-01-01 |12  |10049
3   |234.56      |2009-01-01 |12  |10048
0   |234.56      |2020-01-01 |12  |10048

so to prepare the average dataset i want is group by LAC and beside there is condition for LAC = 0 where it must be separated by month range. the query below is a sample

select N'0 ( 01-06 M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet 
from HerdAnalytics_tbl 
where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) <= 6 

union 

select N'0 ( 07-12 M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet 
from HerdAnalytics_tbl 
where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) > 6 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) <= 12 

union 

select N'0 ( 12 < M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet 
from HerdAnalytics_tbl 
where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) > 12 

union 

select CAST(LAC as varchar),CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet 
from HerdAnalytics_tbl where GRP = 12 and LAC in (select LAC from HerdAnalytics_tbl 
where FARM_FK = 10048 and LAC != 0)  
group by LAC

union 

select 'TOTAL' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet 
from HerdAnalytics_tbl 
where GRP = 12

when i use union to merge them i could not use order by in the 4th query and also it sort by LAC as a varchar data so lac 10 comes after 1 since it is a varchar as shown below

YDS           | DataSet
------------------------
0 ( 01-06 M ) | 117.78
0 ( 07-12 M ) | 465.26
0 ( 12 < M )  | NULL
1             | 292.58
10            | -62.55
2             | 321.40
3             | 278.24
4             | 308.68
5             | 267.48
6             | 229.36
7             | 165.18
8             | 105.14
9             | 65.68
TOTAL         | 149.95

is there any way to sort properly the 4th query

Answer 1

The Order by clause is the only one that guarantee the order.

But if you really want in back end , then you can add some additional columns/attributes to make it easier.
I added a grp = group level and a subgroup grp_2 =group level 2.

For 0 ( 01-06 M ),0 ( 07-12 M ),0 ( 12 < M ), the grp = 0
For monthly records, grp = 1
For TOTAL, grp = 2

And for grp_2, we have: 0 ( 01-06 M )grp_2 = 1,0 ( 07-12 M ) grp_2 = 2,0 ( 12 < M ) grp_2 = 3
For monthly records, grp_2 = LAC
For TOTAL, grp_2 = 0

And so, we are ordering by ORDER BY a.grp,a.grp_2

SELECT a.YDS,a.DataSet
FROM
(
    select N'0 ( 01-06 M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet ,0 as grp,1 as grp_2
    from HerdAnalytics_tbl 
    where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) <= 6 

    union 

    select N'0 ( 07-12 M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet,0 ,2
    from HerdAnalytics_tbl 
    where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) > 6 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) <= 12 

    union 

    select N'0 ( 12 < M )' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet ,0,3
    from HerdAnalytics_tbl 
    where GRP = 12 and LAC = 0 and DATEDIFF(MONTH, FA_BDATE , GETDATE()) > 12 

    union 

    select CAST(LAC as varchar),CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet ,1,Lac
    from HerdAnalytics_tbl 
    where GRP = 12 
        and LAC in (select LAC from HerdAnalytics_tbl where FARM_FK = 10048 and LAC != 0)  
    group by LAC

    union 

    select 'TOTAL' as YDS ,CAST(AVG(FLUID_MERIT) as decimal(10, 2)) AS DataSet ,2,0
    from HerdAnalytics_tbl 
    where GRP = 12
)as a
ORDER BY a.grp,a.grp_2

output:

YDS             DataSet
0 ( 01-06 M )   NULL
0 ( 07-12 M )   NULL
0 ( 12 < M )    234.56
3               234.56
4               234.56
10              234.56
TOTAL           234.56

dbfiddle

Answer 2

The above answer clearly works an alternative (simpler ?) solution would be if you add leading zeros to the varchar YDS representation of the number then everything will sort correctly, simple example below you would probably need to adjust the update to exclude the values like 0 ( 01-06 M ).

create table #t (num int, strnumber varchar(10))

insert #t (num, strnumber) values (2,''), (4,''),(7,''),(21,''),(33,''),(5,''),(8,'')

update #t set strnumber = right('00'+ convert(varchar(10), num), 2)

select *  from #t order by strnumber