如何把多个SELECT语句到不同的列

Question

我基本上有我需要有结果输出到单独的列7的选择语句。通常我会用这个交叉表，但我需要一个快速有效的方式去了解这个，因为在表中有超过7十亿行。我使用的Vertica的数据库系统。下面是我的语句的示例：

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：

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

Answer 1

您可以使用一系列联合在一起的查询在一起。样的难看，但它应该工作

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  

... ETC

Answer 2

将它们包装在括号中，加逗号和选择它们：）

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'

或者你可以做一个标量函数，它的参数date_dim_id并返回你想要的结果，并称之为多次..（如果您的数据库系统支持的标量函数的）

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

那么，可以考虑使用透视表。它更EyeCandy的：）

首先工会的结果，比转动它！

下面有你的例子，这里是的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