MYSQL extends in such a manner that rules are not followed by SQL standards
i am very much found of ***`microsoft technologies`*** and today i see a post 

which
 

[mysql-group-wise-maximum-of-a-certain-column][1]




and in answer somebody writes that answer 


    **Standard SQL** would reject your query because you can not SELECT non-aggregate fields that are not part of the GROUP BY clause in an aggregate query. 

    MySQL extends the use of GROUP BY so that the select list can refer to nonaggregated 
    columns not named in the GROUP BY clause. This means that the preceding query is legal in 
    MySQL. You can use this feature to get better performance by avoiding unnecessary column 
    sorting and grouping. However, this is useful primarily when all values in each 
    nonaggregated column not named in the GROUP BY are the same for each group. The server is 
    free to choose any value from each group, so unless they are the same, the values chosen are **indeterminate**.



which is absolutely right 


***now my question is why*** 


MYSQL extends in such a manner that rules are not followed by ***SQL standards*** 
and second thing why this feature which is ***inderterminate*** by user the result 


  [1]: http://stackoverflow.com/questions/7594465/mysql-group-wise-maximum-of-a-certain-column

MYSQL extends in such a manner that rules are not followed by SQL standards
===

i am very much found of ***`microsoft technologies`*** and today i see a post 

which
 

[mysql-group-wise-maximum-of-a-certain-column][1]




and in answer somebody writes that answer 


    **Standard SQL** would reject your query because you can not SELECT non-aggregate fields that are not part of the GROUP BY clause in an aggregate query. 

    MySQL extends the use of GROUP BY so that the select list can refer to nonaggregated 
    columns not named in the GROUP BY clause. This means that the preceding query is legal in 
    MySQL. You can use this feature to get better performance by avoiding unnecessary column 
    sorting and grouping. However, this is useful primarily when all values in each 
    nonaggregated column not named in the GROUP BY are the same for each group. The server is 
    free to choose any value from each group, so unless they are the same, the values chosen are **indeterminate**.



which is absolutely right 


***now my question is why*** 


MYSQL extends in such a manner that rules are not followed by ***SQL standards*** 
and second thing why this feature which is ***inderterminate*** by user the result 


  [1]: http://stackoverflow.com/questions/7594465/mysql-group-wise-maximum-of-a-certain-column
