Question

我需要更新表并使用以下规则将列（启用）设置为1

每个Employee_Guid必须有1（并且从不0或> 1）记录，启用设置为1。
它应该选择已删除的记录设置为0（应该只有一个或没有删除的记录设置为每个Employee_Guid为0）以将启用设置为1.
如果所有记录都已删除设置为1，则应使用具有最新Create_Date_Time
如果与创建日期时间相关，则可以将任何记录组的记录设置为1，但只能使用其中一个记录。

如果有多个记录已删除设置为0，我希望抛出一个错误，因为这是一个非法状态。

这是我到目前为止所拥有的

if(exists(select count(employee_guid) from Employees_M where deleted = 0 group by employee_guid having count(employee_guid) > 1))
    RAISERROR('More than one record has deleted set to 0')
Update Employees_M set [ENABLE] = 0

select * into #t from employees_m where deleted = 0
insert into #t select * from employees_m where employee_guid not in (select employee_guid from #t) 
                                         and --fulfill rules 3 and 4

Update Employees_M set [ENABLE] = 1
where pk_guid in (select pk_guid from #t)

这是表结构

PK_Guid (primary key, uniuque, uniuqueidenitfier, not null)
Employee_Guid (uniuqueidenitfier, not null)    
Deleted (bit, not null)
Enable (bit, not null)
Create_Date_Time (datetime defaults to getdate(), not null)

这不仅仅是一个“Show me teh codez”的问题。我想学习如何正确地做到这一点，所以也应该赞赏类似但不解决问题的链接或示例。

Answer 1

在这种情况下，通常可以使用row_number。其order by子句允许您分配优先级。在您的情况下，deleted asc和Create_Date desc似乎可以捕获要求。

以下是如何在更新查询中使用row_number的示例：

update  emp
set     enabled = case when rn = 1 then 1 else 0 end
from    (
        select  row_number() over (partition by employee_guid 
                                   order by deleted, Create_Date desc) as rn
        ,       *
        from    @employees
        ) emp

Full example at SE Data.

Answer 2

难题。试试这个，我希望这有效。

if(exists(select 1 from Employees_M where deleted = 0  having count(employee_guid) > 1))
    RAISERROR('More than one record has deleted set to 0')

Update Employees_M E
set [ENABLE] = 1
WHERE EXISTS 
(
  SELECT 1 
  FROM Employees_M  
  WHERE E.employee_guid = employee_guid 
  AND (DELETED = 0 OR DELETED IS NULL)
) --SECOND POINT
OR EXISTS 
(
  SELECT 1 
  FROM Employees_M  
  WHERE E.employee_guid = employee_guid 
  AND ENABLE <> 1 -- 4 POINT 
  AND Create_Date_Time =  
  (
    SELECT DISTINCT(MAX(Create_Date_Time)) 
    FROM Employees_M 
    WHERE E.employee_guid = employee_guid 
  )
  HAVING COUNT(employee_guid) = SUM(deleted) --3 POINT
)

如何编写棘手的更新查询

2 个答案: