Oracle count(1)、count(*)、count(列) 区别详解

1 结论

2 示例

with t_test as (
  select 1 id, null name from dual union all
  select 2 id, 'a'  name from dual union all
  select 3 id, 'a'  name from dual
)
select count(1), -- 3
       count(*),  -- 3
       count(name), -- 2
       count(distinct name) -- 1
  from t_test;