Question

我有以下查询：

SELECT 
num.description,
(num.new_driver_form/denom.form_sent_to) as conversion
FROM
(SELECT
'Common' as description,
count(DISTINCT u1.user_id) as new_driver_form
FROM   
user_tags u1
JOIN   
user_tags u2 USING (user_id)
WHERE  
u1.name = 'sentForm'
AND    
u2.name = 'recForm')num
JOIN
(SELECT
'Common' as description,
count(DISTINCT user_id) as form_sent_to
FROM 
user_tags
WHERE
name = 'sentForm')denom
ON num.description = denom.description

我收到的错误是“未能找到从未知到文本的转换功能”，但我不确定这意味着什么。

Answer 1

这是一种简单的方法

SELECT
  'cohort' as description,
  count(DISTINCT u1.user_id) as new_driver_form,
  x.field as field
FROM user_tags u1
JOIN user_tags u2 USING (user_id)
JOIN anothertable X ON x.blah = u1.blah
WHERE  
  u1.name = 'sentForm'
  AND    
  u2.name = 'recForm'

如果字符串来自其中一个表，那么这样就可以了：

SELECT
  <replace with field name> as description,
  count(DISTINCT u1.user_id) as new_driver_form,
  x.field as field
FROM user_tags u1
JOIN user_tags u2 USING (user_id)
JOIN anothertable X ON x.blah = u1.blah
WHERE  
  u1.name = 'sentForm'
  AND    
  u2.name = 'recForm'

Answer 2

您需要添加显式type cast以避免错误。 'Common'只是一个字符串文字，Postgres希望你提供它应该转换的类型。

您还需要将num.new_driver_form号码SELECT num.description ,(num.new_driver_form::numeric / denom.form_sent_to) AS conversion FROM ( SELECT 'Common'::text AS description ,count(DISTINCT u1.user_id) AS new_driver_form FROM user_tags u1 JOIN user_tags u2 USING (user_id) WHERE u1.name = 'sentForm' AND u2.name = 'recForm' ) num JOIN ( SELECT 'Common'::text AS description ,count(DISTINCT user_id) AS form_sent_to FROM user_tags WHERE name = 'sentForm' ) denom ON num.description = denom.description（bigint）转换为count() returns bigint（或有损浮点类型）以获得有意义的结果divison。然后，您将对numeric函数感兴趣。

JOIN

当然，你的TRUE开始时没有多大意义，因为第二个子查询计算单行而JOIN条件总是SELECT num.description ,(num.new_driver_form::numeric / denom.form_sent_to) AS conversion FROM ( SELECT 'Common'::text AS description ,count(DISTINCT u1.user_id) AS new_driver_form FROM user_tags u1 JOIN user_tags u2 USING (user_id) WHERE u1.name = 'sentForm' AND u2.name = 'recForm' ) num JOIN ( SELECT count(DISTINCT user_id) AS form_sent_to FROM user_tags WHERE name = 'sentForm' ) denom ON TRUE。可以简化为：

SELECT 'Common'::text AS description
      ,(count(DISTINCT u1.user_id)::numeric
       / (SELECT count(DISTINCT user_id)
          FROM   user_tags
          WHERE  name = 'sentForm')) AS conversion
FROM   user_tags u1
JOIN   user_tags u2 USING (user_id)
WHERE  u1.name = 'sentForm'
AND    u2.name = 'recForm'

或者只使用子查询：

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SQL添加用户创建的结果行

2 个答案: