如何将多个 Select 语句放入不同的列中

Question

我基本上有 7 个 select 语句，我需要将结果输出到单独的列中。通常我会为此使用交叉表，但我需要一种快速有效的方法来解决此问题，因为表中有超过 70 亿行。我正在使用vertica数据库系统。以下是我的陈述的示例：

SELECT COUNT(user_id) AS '20100101' FROM event_log_facts WHERE date_dim_id=20100101
SELECT COUNT(user_id) AS '20100102' FROM event_log_facts WHERE date_dim_id=20100102
SELECT COUNT(user_id) AS '20100103' FROM event_log_facts WHERE date_dim_id=20100103
SELECT COUNT(user_id) AS '20100104' FROM event_log_facts WHERE date_dim_id=20100104
SELECT COUNT(user_id) AS '20100105' FROM event_log_facts WHERE date_dim_id=20100105
SELECT COUNT(user_id) AS '20100106' FROM event_log_facts WHERE date_dim_id=20100106
SELECT COUNT(user_id) AS '20100107' FROM event_log_facts WHERE date_dim_id=20100107

应该返回类似以下内容：

20100101 | 20100102 | 20100103 | 20100104 | 20100105 | 20100106 | 20100107
1234     | 1234     | 36564    | 45465    | 356754   | 3455     | 4556675

Answer 1

将它们括在括号中，添加逗号并选择它们:)

SELECT
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100101) AS '20100101',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100102) AS '20100102',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100103) AS '20100103',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100104) AS '20100104',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100105) AS '20100105',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100106) AS '20100106',
(SELECT COUNT(user_id) FROM event_log_facts WHERE date_dim_id=20100107) AS '20100107'

或者您可以创建一个标量函数，该函数将 date_dim_id 作为参数并返回您想要的结果，然后多次调用它..（如果您的数据库系统支持标量函数）

Answer 2

您可以使用一系列联合在一起的查询。有点丑，但应该可以用

SELECT  
  COUNT(user_id) AS '20100101'  
 ,NULL AS '20100102'  
 ,NULL AS '20100103'  
 ,NULL AS '20100104'  
 ,NULL AS '20100105'  
FROM  
  event_log_facts  
WHERE  
  date_dim_id=20100101  
UNION  
SELECT  
  NULL AS '20100101'  
 ,COUNT(user_id) AS '20100102'  
 ,NULL AS '20100103'  
 ,NULL AS '20100104'  
 ,NULL AS '20100105'  
FROM   
  event_log_facts  
WHERE  
  date_dim_id=20100102  
UNION  
SELECT  
  NULL AS '20100101'  
 ,NULL AS '20100102'  
 ,COUNT(user_id) AS '20100103'  
 ,NULL AS '20100104'  
 ,NULL AS '20100105'  
FROM  
  event_log_facts  
WHERE  
  date_dim_id=20100103  

等等......

Answer 3

SELECT
COUNT(date_dim=20100101 OR NULL) AS '20100101',
COUNT(date_dim=20100102 OR NULL) AS '20100102',
...
FROM event_log_facts

Answer 4

好吧，考虑使用数据透视表。它更像是 EyeCandy :)

首先合并你的结果，而不是旋转它！

这是您的示例，这里是 SQLFiddle -> http://sqlfiddle.com/#!6/d41d8/6440

SELECT PivT.* 
FROM
(
  SELECT 10 As Quantity, '20100101' AS DateDim
  UNION
  SELECT 21 , '20100102' 
  UNION
  SELECT 3 , '20100103' 
  UNION
  SELECT 41 , '20100104' 
  UNION
  SELECT 50 , '20100105' 
  UNION
  SELECT 26 , '20100106' 
  UNION
  SELECT 78 , '20100107' 
) T
 PIVOT (avg(Quantity) for DateDim in ([20100101],
                         [20100102],
                         [20100103],
                         [20100104],
                         [20100105],
                         [20100106],
                         [20100107])
) As PivT