如何使用sql查询达到以下要求

Question

  TABLE1               TABLE2
ID   DATE             ID   NAME
1    1 JAN            1    ABC
2    2 JAN            2    ABC
3    3 JAN            3    CDF
4    4 JAN            4    CDF

对表2进行分组，以使id = 1,2和3,4组成2个组，因为1,2具有NAME作为ABC，依此类推。这2个ID = 1,2和3,4的集合将与TABLE1结合在一起，其中TABLE以ID为ID，以在ID = 1,2和ID = 3,4之间搜索最小日期 这样最终结果应该像这样：

ID   DATE    
1   1 JAN 
3   3 JAN

Answer 1

一种使用ROW_NUMBER的方式：

WITH cte AS (
    SELECT t1.ID, t1.DATE,
        ROW_NUMBER() OVER (PARTITION BY t2.NAME ORDER BY t2.ID) rn
    FROM TABLE1 t1
    INNER JOIN TABLE2 t2
        ON t1.ID = t2.ID
)

SELECT ID, DATE
FROM cte
WHERE rn = 1;

Answer 2

您可以简单地使用

select t1.id,t1.date from
 table1 t1 join
(select min(ID) as id,name from
 table2
 group by name
) t2
  on t1.id=t2.id

Answer 3

通常，您可以使用join和group by来做到这一点：

select t2.name, min(t2.date)
from table1 t1 join
     table2 t2
     on t1.id = t2.id
group by t2.name;

这样的查询既不需要子查询，也不需要CTE。

Answer 4

您希望每个名称一个结果行，因此请按名称分组：

select
  min(t2.id) as id,
  min(t1.date) as date
from table1 t1
join table2 t2 on t2.id = t1.id
group by t2.name
order by min(t2.id);

Answer 5

db-fiddle

select id, date
  from table1
 where dt in (select min(date)
                from table1 A
                     left join table2 B
                            on A.id = B.id
               group by name)