連接表的列上用逗號分隔值

Question

表1：mas_book_author

author_id | author_name  
------------+---------------- 
1   | jhon 
2   | roobini 
3   | virat 
4   | sachin 
5   | siva 
6   | priya 

表4：mas_bk_accession_entry

id(int)(pk) | author_ids(varchar) 
-------------+------------------- 
1   | 1,5 
2   | 5,1 
3   | 2,5 
4   | 3,5 
5   | 4,5 

我的結果應該是這樣的：

author_name |count 
------------+------ 
jhon,siva | 2  

這是我的SQL查詢

select b.author_name,COUNT(*) as totbook 
from mas_bk_accession_entry a 
    join mas_book_author as b 
    on b.author_id in (select cast((unnest(string_to_array(f.author_ids,','))) as int) as author_ids 
         from mas_bk_accession_entry f) 
where a.author_ids = '1,5' 
group by b.author_name 

Answer 1

您可以簡化您的加入條件，你需要一個string_agg（）來獲取作者姓名的逗號分隔的列表：

select string_agg(author_name,','), count(*) 
from mas_book_author b 
    join mas_bk_accession_entry e on b.author_id = any(string_to_array(author_ids,',')::int[]) 
where e.author_ids = '1,5'; 

在線例如：http://rextester.com/NVNBH72654

但你確實應該解決您的數據模型。存儲逗號分隔的值，如author_ids列是非常糟糕的選擇。