MYSQL select 连接多个 table 和 SUM

Question

我有三张表

1.master

id_master barcode name last_stock 
1         123     abc  15 
2         234     bcd  10 
3         345     cde  7 
4         456     def  11 
5         567     efg  20

2。 trans_in

id_trans_in barcode qty time_trans 
1           567     1   2016-04-01 10:15:09
2           234     2   2016-04-01 14:15:09
3           345     5   2016-04-01 20:15:09

3。 trans_out

id_trans_out barcode qty time_trans 
1           123     3   2016-04-01 09:15:09
2           234     5   2016-04-01 08:15:09

我必须建立一个查询来给出结果

id_master barcode name last_stock in out
1         123     abc  15         0   3
2         234     bcd  10         2   5
3         345     cde  7          5   0
4         456     def  11         0   0
5         567     efg  20         1   0

我只是在尝试简单的查询

select
    a.id_master, a.barcode, a.name,
    COALESCE(SUM(b.qty),'0')
from
    master a
inner join trans_in b
on a.barcode = b.barcode
where
    date(b.time_trans) = '2016-04-01'   
group by a.barcode

结果是

id_master barcode name COALESCE(SUM(b.qty),'0')
5         567     efg  1
2         234     bcd  2
3         345     cde  5

我不知道如何通过 time_trans（如果为 null 则为 0）合并 master、trans_in 和 trans_out 的完整列表，我已经尝试使用左连接、内连接其中三个，但结果让我头晕.. SUM 的结果超过了字段的数量，我真的不知道为什么。

Answer 1

您可以左连接到一些派生表，以防每个日期有多个条目

    SELECT  a.id_master ,
        a.barcode ,
        a.name ,
        a.last_stock ,
        COALESCE(b.`IN`, 0) AS `IN`,
        COALESCE(c.`OUT`, 0) AS `OUT`
FROM    master a
        LEFT JOIN (SELECT barcode, SUM(qty) as `IN` 
                     FROM trans_in 
                     WHERE date(time_trans) = '2016-04-01' 
                     GROUP BY barcode ) b ON a.barcode = b.barcode
        LEFT JOIN (SELECT barcode, SUM(qty) as `OUT`
                     FROM trans_out 
                     WHERE date(time_trans) = '2016-04-01' 
                     GROUP BY barcode ) c  ON a.barcode = c.barcode;

Answer 2

例如：

SELECT m.* 
     , COALESCE(SUM(CASE WHEN type = 'trans_in' THEN qty END),0) `in`
     , COALESCE(SUM(CASE WHEN type = 'trans_out' THEN qty END),0) `out` 
  FROM master m 
  LEFT 
  JOIN 
     ( SELECT 'trans_in' type
            , id_trans_in id_trans
            , barcode
            , qty
            , time_trans 
         FROM trans_in 
        WHERE time_trans BETWEEN '2016-04-01 00:00:00' AND '2016-04-01 23:23:59' 
        UNION ALL
       SELECT 'trans_out'
            , id_trans_out
            , barcode
            , qty,time_trans 
         FROM trans_out
        WHERE time_trans BETWEEN '2016-04-01 00:00:00' AND '2016-04-01 23:23:59' 
     ) x 
    ON x.barcode = m.barcode
 GROUP 
    BY m.id_master
 ORDER
    BY id_master;

考虑将交易存储在单个 table 中。它将简化和加速这一过程。此外，我假设在 time_trans 上有一个 INDEX，并相应地构建了一个范围查询。

MYSQL select 连接多个 table 和 SUM

MYSQL select join multiple table and SUM

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