我如何将三个表的结果合并为一个结果

Question

我从同一张表中获得以下三个结果，不同的where语句

  SELECT count(*) as LONG_TERM_LEASE_2017_Apirl
  FROM drivenow.rent 
  where (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-04-01' AND '2017-04-30');

SELECT count(*) as LONG_TERM_LEASE_2017_May 
FROM drivenow.rent 
where (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-05-01' AND '2017-05-30');

SELECT count(*) as LONG_TERM_LEASE_2017_June
FROM drivenow.rent
WHERE (rentalterm="both" OR  rentalterm="Long" )AND (created_at BETWEEN '2017-06-01' AND '2017-06-30');

我想在我的SQL结果中并排显示这样的内容

LONG_TERM_LEASE_2017_Apirl|LONG_TERM_LEASE_2017_May|LONG_TERM_LEASE_2017_June

我怎样才能做到这一点？ 对不起，我是编程初学者。

Answer 1

SELECT 
COUNT(CASE WHEN (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-04-01' AND '2017-04-30') then 1 ELSE NULL END) as LONG_TERM_LEASE_2017_Apirl,
COUNT(CASE WHEN (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-05-01' AND '2017-05-30'); then 1 ELSE NULL END) as LONG_TERM_LEASE_2017_May ,
COUNT(CASE WHEN (rentalterm="both" OR  rentalterm="Long" )AND (created_at BETWEEN '2017-06-01' AND '2017-06-30') then 1 ELSE NULL END) as LONG_TERM_LEASE_2017_June
from drivenow.rent ;

Answer 2

您可以cross join这三个Select，但是实际上您只需要使用条件聚合来选择一个Select：

 SELECT
    count(case when created_at BETWEEN '2017-04-01' AND '2017-04-30' then 1 end) as LONG_TERM_LEASE_2017_Apirl,
    count(case when created_at BETWEEN '2017-05-01' AND '2017-05-30' then 1 end) as LONG_TERM_LEASE_2017_May,
    count(case when created_at BETWEEN '2017-06-01' AND '2017-06-30' then 1 end) as LONG_TERM_LEASE_2017_June
  FROM drivenow.rent 
  where (rentalterm="Both" OR rentalterm="Long") 
    AND (created_at BETWEEN '2017-04-01' AND '2017-06-30' );

案例返回的1只是用于计数的虚拟值。 除了count您还可以使用如下所示的总和：

sum(case when created_at BETWEEN '2017-04-01' AND '2017-04-30' then 1 else 0 end)

Answer 3

尝试这样：

select
SUM(case when (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-04-01' AND '2017-04-30') then 1 else 0) as LONG_TERM_LEASE_2017_Apirl,
SUM(case when (rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-05-01' AND '2017-05-30') then 1 else 0) as LONG_TERM_LEASE_2017_May,
SUM(case when (rentalterm="both" OR  rentalterm="Long" )AND (created_at BETWEEN '2017-06-01' AND '2017-06-30') then 1 else 0) as LONG_TERM_LEASE_2017_June
FROM drivenow.rent 
WHERE(rentalterm="Both" OR rentalterm="Long") AND (created_at BETWEEN '2017-04-01' AND '2017-06-30') then 1 else 0)