c# - How create groups with evenly sizes -

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i have table car information dates.

car_id date       <aditional info> 1      20160101 2      20160102 1      20160103 2      20160104 1      20160105 1      20160106 1      20160107 1      20160108 1      20160109 1      20160110

if car has <= 5 records have 1 group. case car_id = 2

if car has <= 10 records have 2 evenly group. case car_id = 1 order date

  • 20160101 - 20160106 group 1
  • 20160107 - 20160110 group 2

if car has '> 10' have 3 evenly distributed groups.

desire output.

car_id date         group_id 1      20160101        1 1      20160103        1 1      20160105        1 1      20160106        1 ------------------------ 1      20160107        2 1      20160108        2 1      20160109        2 1      20160110        2 ------------------------ 2      20160102        1 2      20160104        1

i try ntile() cant make group number dinamic.

sql fiddle demo

select car_id,         "date",        ntile(3) on (partition car_id order "date") group_id table1

bonus points if can done direct on c# linq, otherwise create function on postgres.

aditional info display historic car information on different colors (groups) cars small amount of data appear single color. , max number of colors 3.

you use ntile:

select car_id, "date",         ntile(case when c <= 5 1                    when c <= 10 2                    else 3               end)  on (partition car_id order "date") group_id (select car_id, "date",count(*) over(partition car_id) c       table1) s

sqlfiddledemo

output:

╔════════╦══════════╦══════════╗ ║ car_id ║   date   ║ group_id ║ ╠════════╬══════════╬══════════╣ ║      1 ║ 20160101 ║        1 ║ ║      1 ║ 20160103 ║        1 ║ ║      1 ║ 20160105 ║        1 ║ ║      1 ║ 20160106 ║        1 ║ ║      1 ║ 20160107 ║        2 ║ ║      1 ║ 20160108 ║        2 ║ ║      1 ║ 20160109 ║        2 ║ ║      1 ║ 20160110 ║        2 ║ ║      2 ║ 20160102 ║        1 ║ ║      2 ║ 20160104 ║        1 ║ ╚════════╩══════════╩══════════╝

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