postgresql 字符串分割字段转列表查询

在数据查询中，有一张a表存有另一张b表的id并以‘，’隔开

如：

 

假设现在要关联查询关于 b表的一些信息，怎么办。

分割查询:字符串转列表函数 ：regexp_split_to_table()

select * from regexp_split_to_table ((select product_ids from fee_project_meal where id = 116199376233182210 ), ',')

查询后，字符串就变成了列表，然后你就可以根据这个列表去找b表的相关信息了。

select *
from  pm.product 
where id::text in 
(select * from regexp_split_to_table ((select product_ids from bp.fee_project_meal where id = 116199376233182210 ), ','))

首先数据验证是正确的，说明sql没有问题，接下来就是一起关联查询了

1.因为这个a表与b表是一对多的关系，所以我们先关联出多条。

select a.id as "a表_id",
a.name as "a表_name",
p.name as "b表_name"
from bp.fee_project_meal a
LEFT JOIN pm.product p on p.id::text 
in (select * from regexp_split_to_table ((select product_ids from bp.fee_project_meal where id = a.id ), ','))
where a.id = 116199376233182210

2.还有一种就是 我只要查出a表的数据，b表的数据中某些字段做未拼接的形式存在，也就是说 现在要查出a表的数据

 SELECT
   a.id as "a表_id",
     a.name as "a表_name",
        bb.p_id as "b表_拼接id",
        bb.p_name as "b表_拼接name"
    from bp.fee_project_meal a
        left join (
select a.id as "bb_id",String_agg(p.id::text,',') as "p_id",String_agg(p.name::text,',') as "p_name"
from bp.fee_project_meal a
LEFT JOIN pm.product p on 
p.id::text in (select * from regexp_split_to_table ((select product_ids from bp.fee_project_meal where id = a.id ), ','))
GROUP BY 1
) bb on bb."bb_id" = a.id
  

以上就是，字符串字段的拆解查询。