MySQL: How to optimize this QUERY? Calculating SUM by year(date) -

-

i have query calculating sums of values per every year based on date.

it works, heavy, takes minute 2 minutes running on 10k records

is there way optimize this, or write in more efficient way?

"select departments sum(case when year(employment_date) = '1990' 1 else  0 end) '1990',"     + "sum(case when year(employment_date) = '2010' 1 else  0 end) '2010',"     + "sum(case when year(employment_date) = '2011' 1 else  0 end) '2011',"     + "sum(case when year(employment_date) = '2012' 1 else  0 end) '2012',"     + "sum(case when year(employment_date) = '2013' 1 else  0 end) '2013',"     + "sum(case when year(employment_date) = '2014' 1 else  0 end) '2014',"     + "sum(case when year(employment_date) = '2015' 1 else  0 end) '2015',"      + "sum(case when year(employment_date) = '2016' 1 else  0 end) '2016',"      + " count(departments.dept_id) total "     + "from employees inner join departments on employees.employee_id=departments.employee_id , departments.dept_id = ?";   sample resuts      |departments  | total | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 |     |data systems | 100   | 30   | 10   | 5    | 15   | 20   | 12   | 8    |     |social ssmp  | 70    | 10   | 10   | 15   | 15   | 4    | 6    | 10   |

in mysql, 1 of best way improve query performance indexing.the whole point of having index speed search queries cutting down number of records/rows in table need examined.

create index emp_index on employee (employment_date, employee_id); create index dept_index on departments(departments , dept_id );

please refer link more info.

just quick suggestion.. indexing costs additional writes , storage space, if application requires more insert/update operation, might want use tables without indexes, if requires more data retrieval operations, should go indexed table.


Comments

Post a Comment

Popular posts from this blog

ios - Memory not freeing up after popping viewcontroller using ARC -

-
hi project arc based, using uinavigationcontroller make transition between viewcontroller. using profiler analyse happening behind scene memory. noticed when push viewcontroller allocate memory components , when pop not freeing allocated memory. since using arc unable implement dealloc or release component. have analysed in detail , there no memory leak in project. i not using strong property push viewcontroller. here how pushing viewcontroller. viewcontroller *obj = [[viewcontroller alloc] init]; [self.navigationcontroller pushviewcontroller:obj animated:no]; any clue whats going on? should free memory have consumed. please advise your description indicates have retain cycle, leads objects not being deallocated. typical source of retain cycles properties assigned loading nib files (usually declared iboutlet ). two strategies break them , release objects: declare property weak : @property (nonatomic, weak) iboutlet uilabel *statuslabel; set property nil in...
Read more

Django REST Framework perform_create: You cannot call `.save()` after accessing `serializer.data` -

-
i have following viewset: class artistprofileviewset(viewsets.modelviewset): queryset = artistprofile.objects.all() serializer_class = artistprofileserializer def perform_create(self, serializer): if serializer.is_valid(): serializer.save() with following serializers: class simpleartisttrackserializer(serializers.hyperlinkedmodelserializer): class meta: model = artisttrack fields = (...my fields...) class artistprofileserializer(serializers.hyperlinkedmodelserializer): owners = userserializer(many=true, required=false) tracks = simpleartisttrackserializer(many=true, required=false) class meta: model = artistprofile fields = (...my fields...) i getting following error: assertionerror: cannot call `.save()` after accessing `serializer.data`.if need access data before committing database inspect 'serializer.validated_data' instead. i don't see editing serializer.data object. th...
Read more

Why does Go error when trying to marshal this JSON? -

-
i'm trying rather simple example of trying decode json file structs using golang. however, when attempting error that json: cannot unmarshal object go value of type []main.track which don't understand. here's code in question, , json can found here . package main import ( "encoding/json" "fmt" "net/http" "os" ) // tracks group of track types type tracks struct { tracks []track } // track represents singular track type track struct { name string url string artist artist } // artist represents single artist type artist struct { name string mbid string url string } func main() { url := "http://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&api_key=c1572082105bd40d247836b5c1819623&format=json&country=netherlands" response, err := http.get(url) if err != nil { fmt.printf("%s\n", err) os.exit(1) } de...
Read more