Charindex and temporal tables in SQL

Update #temp

Set #temp. Recycle=case when uniona.num>0 then 1 else 0 end

From (select Gradeid,sum (num) as num from Areaallot

where CHARINDEX (@Area, Areaallot.area) =1 and LEN (@Area) =len (area)-2

Group by Gradeid) Uniona INNER JOIN #temp

On uniona.gradeid= #temp. Gradeid

1, for this charindex today tangled a long time to figure out how to understand is how a meaning, in order to forget later, so probably do a note,

CHARINDEX (@Area, Areaallot.area) =1 also is the starting position of @area in Areaallot.area, equals 1 means the starting position is the first bit, if equals 2 means the starting position is the second bit, and so on, but if equals 0 means @ Area is not included in the Areaallot.area. The following: Select CHARINDEX (' 43 ', ' 414305 ')
Select CHARINDEX (' 43 ', ' 4305 ') 2, I used to think that group by and order by were meant to be a sort, and it was only today that the group by was used for classification.