Tsql 动态重新排序SQL Server表中的列值

我有一个SQL Server用户技能表，每个用户的优先级顺序如下：

+----+------+----------+----------+
| ID | user | skill    | priority |
+----+------+----------+----------+
| 1  | foo  | swimming | 1        |
+----+------+----------+----------+
| 2  | foo  | running  | 2        |
+----+------+----------+----------+
| 3  | foo  | hunting  | 3        |
+----+------+----------+----------+
| 4  | boo  | swimming | 1        |
+----+------+----------+----------+
| 5  | moo  | swimming | 1        |
+----+------+----------+----------+
| 6  | moo  | running  | 2        |
+----+------+----------+----------+

当其中一项技能的优先级值更改时，如何编写SQL代码以将优先级列值重新排序为用户所有技能的整数

例如：对于用户foo，我会将技能游泳的优先级从1更改为2；update语句还必须以动态方式更改该用户所有其他技能的优先级

---

因此，在该示例中，游泳的优先级将是2而不是1，运行的优先级将是1而不是2，其他优先级将保持不变。

在这个答案中，我假设您希望使用SQL而不是C来执行此操作。基于该假设，单个事务中的这两个SQL语句将指定技能的优先级提高1

'Set @User to the required user and @Skill to the required skill.

'Decrease the priority of the user's skill above the specified skill.
UPDATE MyTable
SET    priority = priority + 1
WHERE  user = @User 
AND    priority = (SELECT priority - 1 
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)

'Increase the specified skill's priority.
UPDATE MyTable
SET    priority = priority - 1
WHERE  user = @User
AND    skill = @Skill
AND    priority > 1

以类似的方式，这两条SQL语句将指定的技能提高到指定的优先级

'Set @User to the required user and @Skill to the required skill.
'Set @NewPriority to the new priority.

'Decrease the higher-prioritised skills.
UPDATE MyTable
SET    priority = priority + 1
WHERE  user = @User 
AND    priority >= @NewPriority 
AND    priority < (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)

'Set the specified skill's priority as requested.
UPDATE MyTable
SET    priority = @NewPriority 
WHERE  user = @User
AND    skill = @Skill
AND    priority > 1

'Set @User to the required user and @Skill to the required skill.
'Set @NewPriority to the new priority.

'Decrease the higher-prioritised skills to
'handle case where new priority is higher.
UPDATE MyTable
SET    priority = priority + 1
WHERE  user = @User 
AND    priority >= @NewPriority 
AND    priority < (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)

'Increase the lower-prioritised skills to
'handle case where new priority is lower.
UPDATE MyTable
SET    priority = priority - 1
WHERE  user = @User 
AND    priority <= @NewPriority 
AND    priority > (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)    

'Set the specified skill's priority as requested.
UPDATE MyTable
SET    priority = @NewPriority 
WHERE  user = @User
AND    skill = @Skill

这三条SQL语句将指定的技能移动到指定的优先级

'Set @User to the required user and @Skill to the required skill.
'Set @NewPriority to the new priority.

'Decrease the higher-prioritised skills.
UPDATE MyTable
SET    priority = priority + 1
WHERE  user = @User 
AND    priority >= @NewPriority 
AND    priority < (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)

'Set the specified skill's priority as requested.
UPDATE MyTable
SET    priority = @NewPriority 
WHERE  user = @User
AND    skill = @Skill
AND    priority > 1

'Set @User to the required user and @Skill to the required skill.
'Set @NewPriority to the new priority.

'Decrease the higher-prioritised skills to
'handle case where new priority is higher.
UPDATE MyTable
SET    priority = priority + 1
WHERE  user = @User 
AND    priority >= @NewPriority 
AND    priority < (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)

'Increase the lower-prioritised skills to
'handle case where new priority is lower.
UPDATE MyTable
SET    priority = priority - 1
WHERE  user = @User 
AND    priority <= @NewPriority 
AND    priority > (SELECT priority
                   FROM MyTable 
                   WHERE user = @User
                   AND skill = @Skill)    

'Set the specified skill's priority as requested.
UPDATE MyTable
SET    priority = @NewPriority 
WHERE  user = @User
AND    skill = @Skill

---

其他一些示例将很有帮助，特别是对于边缘情况。例如：如果foo/swiming的优先级更改为0，那么foo/running是否应该为1？如果foo/swiming更改为5，该怎么办？SQL Server不会以任何特定顺序存储或检索项。查询是使用微处理器中的不同内核并行完成的，因此必须始终使用OrderBy对结果进行排序。@jdweng，这个问题与行的存储或检索顺序无关。它是关于为一个用户的每一行分配新的优先级值，每当该用户的一个优先级值被更改时。@HABO，第一个答案是处理行删除后的重新排序。这个问题是关于普通的重新排序，不删除行。@HABO，至于您链接的第二个答案，SQL代码确实很长，很复杂，而且通常很糟糕。我甚至不确定它是否正确。在问题评论中进一步澄清后，OP似乎希望能够对一项技能的优先级进行更新，使其位于用户拥有n项技能的1-n范围内的任何位置。然后，所有其他技能的优先级应根据需要向上或向下调整，以填充该范围1-n中的其余值。@Richard，我已添加代码以满足此要求。@RoadWarrior根据我从您的代码中了解，我应该使用存储过程中的最后一部分——三条语句，因为它替换了前两部分中的旧答案？@Sherif，与我在前两个代码部分中提到的其他更简单的用例不同，如果您想将某项技能的优先级重新分配到任何位置，这是正确的。@如果您想使操作原子化，请注意单个事务中的SQL语句。