help me in understanding this update statement

[aakcse]

Help needed in understanding the below update statement

update results_key set 

result = temp.tally

from(

        select testid,result,count(*) as tally

        from reslults_emp

        where testid='e001'

     ) temp

where resluts_key.testid=temp.testid

and results_key.value=temp.result

According to me result expect one and only one value from temp.tally

but it is returning 2 values and the update is working perfectly

updating 2 records.



why I am confused is because I have back ground of Oracle sql plsql and in Oracle

update this is not possible it will give error stating too many rows.



can any body explain me this update statement



Thanks

aak.

[debasisdas]

you need to deeply look into the join part for your answer.