SQL 计数产品

Question

我有桌子：

name    product
john     beer
john     milk
john     tea
john     beer
emily    milk
emily    milk
emily    tea
john     beer

我需要从这个表中选择，当输出是：

name count(tea)  count(beer) count(milk)  count(total)
john    1             3          1              5
emily   1             0          2              3

知道怎么做吗？

数据库：甲骨文 12

Answer 1

使用条件聚合：

select name
    sum(case when product = 'tea' then 1 else 0 end) cnt_tea,
    sum(case when product = 'beer' then 1 else 0 end) cnt_beer,
    sum(case when product = 'milk' then 1 else 0 end) cnt_milk,
    count(*) total
from mytable
group by name

根据您的数据库，可能有更简洁的选项可用于表达条件计数。