计算和划分SQL中多个列的不同值对

Question

I'm new to SQL and having trouble looking for a query that can produce the last output table.

Example table of what I have:

ID      Color
=============
0       red
0       red
0       blue
1       red
1       yellow
1       yellow

Now with this query I can produce this table

SELECT id, color, count(*) as num
from table group by id,color 

ID      Color      num    
=======================
0       red         2
0       blue        1
1       red         1
1       yellow      2

And with this query I can produce this table

SELECT id, count(*) as num
from table group by id

ID      num    
============
0        3
1        3

But I'm looking to have an output like this. So I'm trying to figure out a way to combine those two above queries to produce this output table.

ID      Color      num    
=======================
0       red         0.667 = 2/3 
0       blue        0.333 = 1/3
1       red         0.333 = 1/3
1       yellow      0.667 = 2/3

Answer 1

You can use the count window function in dividing those values.

SELECT distinct id, color, 
1.0*count(*) over(partition by color,id)/count(*) over(partition by id) as num
from table