sql - SQL中同一列的百分比

Question

我需要用SQL计算总数的百分比我有

customerID, quantity

我尝试过的是:

SELECT 
   customer_id, 
   sum(quantity) / (quantity * 100)
FROM MyTable
Group by customer_id

Answer 1

您需要总计来计算百分比，因此请使用子查询。为了避免再次计算每个用户的总数，请交叉连接到一次计算的总数:

select customer_id, quantity * 100 / total
from MyTable 
cross join (
    select sum(quantity) total
    from MyTable) x