postgres中的反向关系答案

【问题标题】：reverse relation in postgrespostgres中的反向关系
【发布时间】：2021-06-29 23:47:58
【问题描述】：

我的数据库“textDate”中有表格

class TextData extends BaseEntity{
 
id(primaryGeneratedColumn)

ar:string

en:string

}

此实体用于存储我的项目中的所有文本，如标题、描述和其他字段都有外键

class object extends baseEntity{

id

@OneToOne()
@joinColumn()
title:TextData
...

由于某些条件，我需要在文本数据中搜索并从中获取记录，并且我想获取对该 textData 记录具有 Fk 的对象注意：有几种类型的对象可以访问文本数据 object1(title),car(title),career(title) 他们都有fk到文本数据...... 有什么事情要做吗？我做了

 select 'post' as Type,p3 .id 
from post p3  
where p3."tagsId" =any ('{1,2,3}') or p3."titleId" =any ('{1,2,3}') 
 join text_data td 
 on td.id =p3."titleId" as  titil
UNION  
select 'career' as Type,c2 .id 
from career c2 
join text_data td 
 on td.id =c2."titleId" as  titil
where c2."tagsId" =any ('{1,2,3}')

【问题讨论】：

标签： typescript postgresql reverse typeorm

【解决方案1】：

您可以在 text_data 中保存对子表的引用，例如子表的名称。

您的查询有一些错误：

select 'post' as Type, p3.id 
from post p3  
join text_data td on td.id = p3."titleId"
where p3."tagsId" = any('{1,2,3}') or p3."titleId" = any('{1,2,3}')

UNION  

select 'career' as Type, c2.id 
from career c2 
join text_data td on td.id = c2."titleId" 
where c2."tagsId" = any('{1,2,3}')

另一种查询方式：

SELECT td.id, coalesce(p3.type, c2.type) AS type

FROM text_data td

INNER JOIN (SELECT "titleId", 'post' AS type FROM post WHERE "tagsId" = any('{1,2,3}') or "titleId" = any('{1,2,3}')) AS p3 ON td.id = p3."titleId"

INNER JOIN (SELECT "titleId", 'career' AS type FROM career WHERE "tagsId" = any('{1,2,3}')) AS c2 ON td.id = c2."titleId"

【讨论】：