Question

嗨，我有一个像这样的桌子：

SN  | User | is_borrowed | date
105 |  1   |      1      |2019-1-1
105 |  1   |      0      |2019-2-1
105 |  1   |      1      |2019-3-1
106 |  2   |      1      |2019-4-1
107 |  1   |      1      |2019-5-1
106 |  2   |      0      |2019-6-1
106 |  2   |      1      |2019-8-1
107 |  1   |      0      |2019-9-1
107 |  2   |      1      |2019-10-1

想要的输出将显示借用的内容（未返回），并且user = 1：

SN  | User | is_borrowed | date
105 |  1   |      1      |2019-3-1

User = 2的输出并借用（未返回）：

SN  | User | is_borrowed | date
106 |  2   |      1      |2019-8-1
107 |  2   |      1      |2019-10-1

总而言之，我想要一个当前借用的设备列表，这些设备未为每个用户返回。可悲的是，我什么都没想到：/

Answer 1

期待您的预期结果似乎是您正在为SN（is_borrowed = 1的用户）寻找max（date）

select SN, user, is_borrowed,  max(date)
from my_table 
where is_borrowed = 1 
group by  SN, user, is_borrowed

或实际借用的设备

Select * from my_table m
inner join t (
  select SN, is_borrowed,  max(date) max_date 
  from my_table 
  where is_borrowed = 1 
  group by  SN,  is_borrowed
) t on t.SN =  m.SN AND t.max_date = m.date

Answer 2

SELECT t.sn, t.user, t.is_borrowed, t.date
FROM TABLE_NAME t
WHERE t.is_borrowed = 1
AND t.date =
              ( 
                  SELECT MAX(x.date)
                  FROM TABLE_NAME x
                  WHERE x.user = t.user
              )
AND (
     SELECT xx.is_borrowed
     FROM TABLE_NAME xx
     WHERE t.sn = xx.sn
     AND t.date < xx.date
     ) <> 0
;

选择每个最新行以获取特定值

2 个答案: