Question

临时订购表

temp_id     series_id   news_ticket_breakdown_id    quantity    expiry_time
58db09bba25b4   2                  2                     2       1490750973
58db09bba25b4   2                  4                     1      1490750973

新闻资讯表

news_id   series_id      news_title
   26          2         GENERIC TICKETING
   27          2         GENERIC TICKETING

当我在series_id上进行左连接时，我返回4行，我只想要2.我不确定如何将连接的行数限制为一行。

CURRENT QUERY

SELECT 
    * 
FROM 
    ticket_ordering_temp    
LEFT JOIN 
    news_items 
on 
    ( news_items.series_id = SELECT 
                                DISTINCT(event_id)
                             FROM 
                                news_items 
                             where 
                                series_id=ticket_ordering_temp.series_id
    )
where 
    temp_id='58db09bba25b4''

期望的结果我只想从表2中获取1行，而不是如上所述连接的2行

temp_id     series_id   news_ticket_breakdown_id    quantity    expiry_time news_title
58db09bba25b4   2                  2                     2       1490750973  GENERIC TICKETING
58db09bba25b4   2                  4                     1      1490750973 GENERIC TICKETING

Answer 1

对于您的样本数据和您想要的结果，您可以尝试按照以下步骤进行操作：

SELECT 
    ticket_ordering_temp.*, t.news_title
FROM 
    ticket_ordering_temp    
LEFT JOIN( 
    SELECT DISTINCT series_id, news_title
    FROM news_items
) t ON ticket_ordering_temp.series_id = t.series_id
WHERE temp_id = '58db09bba25b4'

但是，我认为你应该告诉我们这些样本数据背后的逻辑。

Demo in SqlFiddle

Answer 2

尝试使用tempTable进行查询：

select distinct * from
(select  * from 
(select '58db09bba25b4' as temp_id,   2 as series_id,2 as news_ticket_breakdown_id,2 as quantity,1490750973 as  expiry_time  union all
select '58db09bba25b4' ,  2   ,              4  ,                  1,     1490750973) as tbl_order) as tbl_order

left join


(select series_id,news_title from 
(select  26 as  news_id,         2 as series_id,         'GENERIC TICKETING' as news_title union all
select   27  ,        2 ,        'GENERIC TICKETING') as tbl_items) tbl_items
on tbl_order.series_id = tbl_items.series_id where temp_id ='58db09bba25b4'

使用实际表格查询：

select DISTINCT * from
(select temp_id,series_id,news_ticket_breakdown_id,quantity,expiry_time from tbl_order) as tb_order
left join
(select series_id,news_title from tbl_items) as tb_items
on tb_order.series_id = tb_items.series_id where temp_id ='58db09bba25b4'

结果：

58db09bba25b4   2   2   2   1490750973  2   GENERIC TICKETING
58db09bba25b4   2   4   1   1490750973  2   GENERIC TICKETING

只是提供另一种解决方案。

我试图从LEFT JOIN中获取一行

2 个答案: