mysql - Returns a list of all users, paired with their most "popular" follower. The more followers someone has, the more "popular" they are -


find "popular" follower persons. more followers has, more "popular" are.

i need sql query select popular follower of people.

my table - (followers)

id | person_id | follower_person_id 1    1            2 2    1            3 3    2            1 4    2            4 5    3            1 6    3            2 7    3            4 8    4            3

person_id 1 has total 2 follower (person_id 2, person_id 3), person_id 2 has total 2 followers (person_id 1, person_id 4), person_id 3 has total 3 followers (person_id 1, person_id 2, person_id 4)and person_id 4 has total 1 followers (person_id 3).

therefore, person_id 3 popular follower person_id 1, person_id 1 popular follower person_id 2, person_id 1 (or person_id 2) popular follower person_id 3 , person_id 3 popular person_id 4.

here query... 

select t1.person_id, t1.follower_person_id, t2.cnt followers t1 join (    select person_id, count(*) cnt    followers    group person_id  ) t2  on t1.follower_person_id = t2.person_id t1.person_id = 1 order t2.cnt desc limit 1

above query output is

person_id, follower_person_id, cnt ----------------------------------- 1,         3,                  3

here explanation of above query

this query work find popular person specific person want find paired "popular" follower person.

so output should like

person_id, follower_person_id, cnt ----------------------------------- 1,         3,                  3 2,         1,                  2 3,         1,                  2 4,         3,                  3

now have person table

id | name  1    john          2    ali          3    rohn          4    veronica

now want convert id person name.

final output shoud like

person_name, follower_person_name, cnt -------------------------------------- john,        rohn,                 3 ali,         john,                 2 rohn,        john,                 2 veronica,    rohn,                 3

i need sql query data.

you can use following query:

select person_name, follower_name, cnt (    select person_name, follower_name, cnt,           @rn := if(@pname = person_name, @rn + 1,                     if(@pname := person_name, 1, 1)) rn    (       select t3.name person_name, t4.name follower_name, t2.cnt       followers t1       join (          select person_id, count(*) cnt          followers          group person_id        ) t2  on t1.follower_person_id = t2.person_id       join person t3 on t1.person_id = t3.id       join person t4 on t1.follower_person_id = t4.id       ) x    cross join (select @rn := 0, @pname := '') vars    order person_name, cnt desc) v v.rn = 1;

output:

person_name follower_name   cnt -------------------------------- john        rohn            3 veronica    rohn            3 ali         john            2 rohn        ali             2

the query uses variables in order greatest-per-group record.

demo here


Comments

Post a Comment

Popular posts from this blog

c# - Update a combobox from a presenter (MVP) -

i using mvp in project, new in mvp. have 2 comboboxes. when select option in combobox, combobox should filled new data. this action in presenter. view 'view1' in presenter, , introduced combobox1 , combobox2 properties in 'view1', because need 'datasource', 'displaymember', 'valuemember' , 'refresh()' in method below. but, when using pattern, enough send property like public string combobox2 { { return combobox1.selectedvalue.tosstring(); } } into presenter not whole combobox. how can solve problem? public void onselectedindexchangedcombobox1() { if (view1.combobox1.selectedindex == -1) { return; } datatable dt = tools.getdatatable("a path"); var query = (from o in dt.asenumerable() o.field<string>("afield") == farmerview.combobox1.selectedvalue.tostring() orderby o.field<string>("anotherfield") select...
Read more

How to understand 2 main() functions after using uftrace to profile the C++ program? -

i trying uftrace profile following simple c++ program: #include <iostream> class { public: a() {std::cout << "a created" << std::endl;} ~a() {std::cout << "a destroyed" << std::endl;} }; int main() { a; return 0; } the profile result this: # uftrace a.out created destroyed # duration tid function 2.026 [ 4828] | __cxa_atexit(); [ 4828] | main() { [ 4828] | __static_initialization_and_destruction_0() { 89.397 [ 4828] | std::ios_base::init::init(); 0.768 [ 4828] | __cxa_atexit(); 93.029 [ 4828] | } /* __static_initialization_and_destruction_0 */ 94.425 [ 4828] | } /* main */ [ 4828] | main() { [ 4828] | a::a() { 11.104 [ 4828] | std::operator <<(); 10.825 [ 4828] | std::basic_ostream::operator <<(); 24.514 [ 4828] | } /* a::a */ [ 4828] | a::~a() { 0.978 [ 4828] | ...
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more