想象一下,我有一个CTE,它创建一个包含我需要的所有信息的结果集,并且需要对结果集进行一堆条件计数。有比一堆子查询更好的方法吗?
我也不能使用count() over ()
,因为有时需要对值进行不同的计数,而使用case when val=true then 1 else null end
进行有条件的计数并不能使我清楚地进行计数,更不用说它是基本上与执行一堆子查询相同。
任何建议,还是要创建一堆子查询?
表定义
create table person (id int, name varchar2(20), age int, cityID int);
create table city (id int, name varchar2(20), stateID int);
create table state (id int, name varchar2(20));
insert into person values(1, 'Bob', 45, 1);
insert into person values(2, 'Joe', 33, 1);
insert into person values(3, 'Craig', 20, 1);
insert into person values(4, 'Alex', 45, 2);
insert into person values(5, 'Kevin', 33, 3);
insert into city values(1, 'Chicago', 1);
insert into city values(2, 'New York', 2);
insert into city values(3, 'Los Angeles', 3);
insert into state values(1, 'Illinois');
insert into state values(2, 'New York');
insert into state values(3, 'California');
SQL查询示例
with cte as (
select p.name pName
, p.age pAge
, c.name cName
, s.name sName
from person p
inner join city c
on p.cityID = c.ID
inner join state s
on c.stateID = s.ID
)
select distinct
(select count(*) from cte) totalRows
, (select count(*) from cte where pAge = 45) total45YO
, (select count(*) from cte where cName like 'Chicago') totalChicago
, (select count(distinct cName) from cte) totalCities
from cte
我希望得到的示例输出
TOTALROWS TOTAL45YO TOTALCHICAGO TOTALCITIES
------------------------------------------------------
5 2 3 3
答案 0 :(得分:2)
最简单的方法就像@jarlh提到的那样,并通过用例/和组合来完成,如下所示。
SQL> select count(*) totalRows
2 , sum(case when p.age=45 then 1 else 0 end) total45YO
3 , sum(case when c.name like 'Chicago' then 1 else 0 end) totalChicago
4 , count(distinct c.name) totalCities
5 from person p
6 inner join city c
7 on p.cityID = c.ID
8 inner join state s
9 on c.stateID = s.ID;
TOTALROWS TOTAL45YO TOTALCHICAGO TOTALCITIES
____________ ____________ _______________ ______________
5 2 3 3
SQL>