SQL - 连接两个表或在一列中生成序列

Question

我有 2 个表，Table1 有 OrderNo 和 OrderItemId，Table2 有 OrderNo 和 Linenum。我需要制作显示 orderno、orderItemid 和 Linenum 的临时表。我怎样才能达到预期的结果。 如果无法加入，那么我们也可以针对 Order 生成 OrderItemId 数量的序列。假设 Order 有 5 个 OrderItemId，那么我们可以有从 1 到 5 的系列，下一个订单的系列将从 1 开始，直到关联的 Orderitemid 总数。

我试过这个，但系列没有正确生成。它不是明智的

Select Orderitemid, table1.OrderNo,  
SELECT ROW_NUMBER() OVER(ORDER BY table2.ORDERNO ASC)*1000 AS Linenum 
from Table1 inner join Table2
on table1.Orderno = table2.Orderno

Answer 1

也许你正在寻找这样的东西：

select table1.OrderNo
       , table1.Orderitemid
       , ROW_NUMBER() OVER(partition by table1.OrderNo ORDER BY table1.ORDERNO ASC) AS Linenum 
from Table1 
left join Table2 on table1.OrderNo = table2.OrderNo
group by table1.OrderNo, table1.Orderitemid

您只能对 table2 进行分组：

select table1.OrderNo
       , table1.Orderitemid
       , ROW_NUMBER() OVER(partition by table1.OrderNo ORDER BY table1.ORDERNO ASC) AS Linenum 
from Table1 
left join (select OrderNo 
           from Table2 
           group by OrderNo) table2 on table1.OrderNo = table2.OrderNo

或者只使用 distinct：

select table1.OrderNo
       , table1.Orderitemid
       , ROW_NUMBER() OVER(partition by table1.OrderNo ORDER BY table1.ORDERNO ASC) AS Linenum 
from Table1 
left join (select distinct OrderNo 
           from Table2 ) table2 on table1.OrderNo = table2.OrderNo

或者如果table2没有连接就不想生成Linenum的话可以加case when then else end

select table1.OrderNo
       , table1.Orderitemid
       , case when table2.OrderNo is not null then
                  ROW_NUMBER() OVER(partition by table1.OrderNo ORDER BY table1.ORDERNO ASC)
              else
                  null
              end Linenum
from Table1 
left join (select distinct OrderNo 
           from Table2 ) table2 on table1.OrderNo = table2.OrderNo

这是一个演示：

DEMO

Answer 2

我认为你只需要一个case 表达式：

Select Orderitemid, table1.OrderNo,
       (case when t2 is not null
             then row_number() over (partition by t1.orderno order by t1.orderitemid)
        end) as linenum
from Table1 t1 left join
     (select distinct t2.orderno
      from Table2 t2
     ) t2
     on t1.Orderno = t2.Orderno;

也就是说，当第二个表中有匹配项时，您只需要行号。