Question

我想使用IF（）函数将某些列值转换为列和CONCAT（）函数，但我不能以某种方式正确。我运行这个sql之后：

SELECT 

IF( meta_key =  'property_id',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_id,
IF( meta_key =  'property_contract',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_contract,
IF( meta_key =  'property_agents',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_agents


FROM wp_postmeta

WHERE property_id !='faslse'
and property_agents = 'John Doe'

我收到此错误： 1054 - 'where子句'中的未知列'property_id'

编辑：

我正在尝试此查询但返回0行...

select *

from
(  select
  IF( meta_key =  'property_id',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_id,
  IF( meta_key =  'property_contract',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_contract,
  IF( meta_key =  'property_agents',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_agents

from
  wp_postmeta) p


WHERE 
 p.property_id != 'false'
  and p.property_contract != 'false'
  and p.property_agents!= 'false'

Answer 1

别名在where子句之后应用，因此您有两个选择，重复IF子句：

select
  IF( meta_key =  'property_id',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_id,
  IF( meta_key =  'property_contract',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_contract,
  IF( meta_key =  'property_agents',  CONCAT(meta_key, ' ', meta_value),  'false' ) AS property_agents

from
  wp_postmeta
where
  IF( meta_key =  'property_id',  CONCAT(meta_key, ' ', meta_value),  'false' ) !='faslse'
  and IF( meta_key =  'property_agents',  CONCAT(meta_key, ' ', meta_value),  'false' ) = 'John Doe'

或使用子查询：

select *
from
  (
     select
       IF(...) as property_id,
       IF(...) as property_agents
     from
       wp_postmeta
  ) s
where
  s.property_id != 'false'
  and s.property_agents = 'John Doe'

可以通过各种方式优化查询，但这取决于您的要求。

修改

从问题中不清楚，但我认为你想要解决的问题有点不同。我想你的post_id表中有一个wp_postmeta字段，我想每个帖子的属性都在不同的行中。通过以下查询，您可以获得单个帖子的ID，合同和代理：

select post_id, max(case when meta_key = 'property_id' then CONCAT(meta_key, ' ', meta_value) end) as property_id, max(case when meta_key = 'property_contract' then CONCAT(meta_key, ' ', meta_value) end) as property_contract, max(case when meta_key = 'property_id' then CONCAT(meta_key, ' ', meta_value) end) as property_agents from wp_postmeta group by post_id

然后您可以添加具有以下内容的过滤器：

having property_agents='property_agents John Doe'

Answer 2

而不是

WHERE property_id !='faslse'

请使用此功能，同时更正从faslse到false

的拼写错误

HAVING property_id !='faslse'

从MySQL documentation

复制

您可以在GROUP BY，ORDER BY或HAVING子句中使用别名

Answer 3

请代表“WHERE”条款使用“HAVING”条款

Answer 4

问题就像@fthiella所说的价值观因为我选择的是同一个，所以不能同时是非假的用于执行IF（）语句的列。所以经过一番思考后我想出了这个：

SELECT 
p_id.property_id ,
p_agents.property_agents,
p_contract.property_contract
FROM

(SELECT post_id , IF( meta_key =  'property_contract', meta_value ,  'false' ) AS property_contract FROM wp_postmeta HAVING  property_contract != 'false' )p_contract
INNER join
(SELECT post_id , IF( meta_key =  'property_agents', meta_value ,  'false' ) AS property_agents FROM wp_postmeta HAVING  property_agents != 'false' )p_agents
ON
p_contract.post_id = p_agents.post_id
INNER join
(SELECT post_id , IF( meta_key =  'property_id', meta_value ,  'false' ) AS property_id FROM wp_postmeta HAVING  property_id != 'false' )p_id
ON
p_contract.post_id = p_id.post_id
GROUP BY p_contract.post_id Order by p_contract.post_id

它有效。谢谢大家的努力和帮助。

使用CONCAT（）将列值合并到一列中

4 个答案: