更新来自其他表的表值，如分布

Question

我有一个table 1，我必须从其他桌子table 2 分配奖品，但以先到先得的方式从其他桌子行。

Table 1
ATTIME    | Absent | LeaveType
-----------------------------
2019-01-01| 1      | 
2019-01-02| 1      | 
2019-01-03| 1      | 
2019-01-04| 1      | 
2019-01-05| 1      | 
2019-01-06| 1      | 

Table 2
LeaveType | Total  
-------------------
Casual    | 3   
Sick      | 2

我已经通过使用游标实现了它，但是想要一个设置基 UPDATE QUERY 或任何其他优化我的执行计划的选项，

最终结果将是......

Table 1

ATTIME    | Absent | LeaveType
-----------------------------
2019-01-01| 1      | CL
2019-01-02| 1      | CL
2019-01-03| 1      | CL
2019-01-04| 1      | SL
2019-01-05| 1      | SL
2019-01-06| 1      |

Answer 1

在受支持的 SQL Server 版本中，您将使用累积和 row_number()：

with toupdate as (
      select t1.*,
             row_number() over (order by attime) as seqnum
      from table1 t1
     )
update toupdate
    set leavetype = t2.leavetype
    from (select t2.*,
                 sum(total) over (order by leavetype) as runningtotal
          from table2 t2
         ) t2
    where toupdate.seqnum between t2.runningtotal + 1 - total and t2.runningtotal;

在旧的、不受支持的 SQL Server 版本中，累积和更麻烦。一种方法使用相关子查询：

with toupdate as (
      select t1.*,
             row_number() over (order by attime) as seqnum
      from table1 t1
     )
update toupdate
    set leavetype = t2.leavetype
    from (select t2.*,
                 (select sum(total)
                  from table2 tt2
                  where tt2.leavetype <= t2.leavetype
                ) as runningtotal
          from table2 t2
         ) t2
    where t1.seqnum between t2.runningtotal + 1 - total and t2.runningtotal;