如何從其中value1和value2字段忽略value2字段的表中獲取value1的最大值

Question

我的表具有column1 =日期，column2 = A / B，column3 = id。 我想要的結果是，與ID比較的最新日期應為column2中的B，如果A則忽略

表

C1        C2    C3
10/6/19   A      1
12/6/19   B      1
13/6/19   A      2
09/6/19   A      3
03/6/19   B      1
04/6/19   B      2
12/6/19   B      4
03/6/19   A      5
06/6/19   B      3

預期結果

C3 1 - Valid . Because last value of latest date is B
C3 4 - Valid . Because last value of latest date is B
C3 3 - Invalid. Because last value of latest date is A

Answer 1

使用相關子查詢

DEMO

select * from t1 a
where c1 =(select max(c1) from t1 b where a.c3=b.c3 )
and c2='B'

OUTPUT：

c1         c2   c3
2012-06-19  B   1
2012-06-19  B   4

Answer 2

假設c1列為有效日期，您可以嘗試對max（c1）使用子查詢

select  * 
from my_table m 
inner join  (
  select  id,  max(c1) max_c1 
  from my_table  
  group by id  
) t on t.max_c1 = m.c1 and m.c2='A' and t.id = m.id

或者，如果您還需要與您的ID不匹配的ID，請附加uisng UNION

select  * 
from my_table m 
inner join  (
  select  id,  max(c1) max_c1 
  from my_table  
  group by id  
) t on t.max_c1 = m.c1 and m.c2='A'
select  * 
from my_table m 
inner join  (
  select  id,  max(c1) max_c1 
  from my_table  
  group by id  
) t on t.max_c1 = m.c1 and m.c2='A' and t.id = m.id 

union 

select  max(c1), c2, id
  from my_table where id not in (
  select id 
  from my_table m 
  inner join  (
    select  id,  max(c1) max_c1 
    from my_table  
    group by id  
  ) t on t.max_c1 = m.c1 and m.c2='A'
select  * 
  from my_table m 
  inner join  (
    select  id,  max(c1) max_c1 
    from my_table  
    group by id  
  ) t on t.max_c1 = m.c1 and m.c2='A' and t.id = m.id 
)
group by c2, id

Answer 3

如果只希望將c3值與指標一起使用，則可以使用聚合：

select c3,
       (case when group_concat(c2 order by c1 desc) like 'B,%'
             then 'Valid'
             else 'Invalid'
        end) as flag
from t
group by c3;