Sql 使用X和U锁在同一个表上的死锁

我有一个存储过程，在Begin和Commit tran下有以下两个事务

UPDATE  mytable
SET     UserID = @ToUserID
WHERE   UserID = @UserID 

DELETE  FROM mytable
WHERE   UserID = @UserID 

在多次执行存储过程时，我会死锁。下面是死锁图：

<deadlock-list>
    <deadlock victim="process16409057468">
        <process-list>
            <process id="process16409057468" taskpriority="0" logused="912" waitresource="RID: 6:1:2392:152" waittime="3022" ownerId="6283339" transactionname="user_transaction" lasttranstarted="2019-02-08T21:08:24.663" XDES="0x16401b98490" lockMode="U" schedulerid="8" kpid="23924" status="suspended" spid="92" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2019-02-08T21:08:24.667" lastbatchcompleted="2019-02-08T21:08:24.667" lastattention="1900-01-01T00:00:00.667" clientapp=".Net SqlClient Data Provider" hostname="GYAAN" hostpid="5624" loginname="sa" isolationlevel="read uncommitted (1)" xactid="6283339" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
                <executionStack>
                    <frame procname="mytable" line="377" stmtstart="33320" stmtend="33540" sqlhandle="0x030006004f6bf63211085201eaa9000001000000000000000000000000000000000000000000000000000000">
                        UPDATE  mytable
                        SET     UserID = @ToUserID
                        WHERE   UserID = @UserID      
                    </frame>
                </executionStack>
                <inputbuf>
                    Proc [Database Id = 6 Object Id = 855010127]    
                </inputbuf>
            </process>
            <process id="process163feab3088" taskpriority="0" logused="912" waitresource="RID: 6:1:2392:149" waittime="99" ownerId="6282851" transactionname="user_transaction" lasttranstarted="2019-02-08T21:08:22.107" XDES="0x16401b20490" lockMode="U" schedulerid="3" kpid="33220" status="suspended" spid="81" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2019-02-08T21:08:22.103" lastbatchcompleted="2019-02-08T21:08:22.107" lastattention="1900-01-01T00:00:00.107" clientapp=".Net SqlClient Data Provider" hostname="GYAAN" hostpid="5624" loginname="sa" isolationlevel="read uncommitted (1)" xactid="6282851" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
                <executionStack>
                    <frame procname="mytable" line="382" stmtstart="33650" stmtend="33848" sqlhandle="0x030006004f6bf63211085201eaa9000001000000000000000000000000000000000000000000000000000000">
                        DELETE  FROM mytable
                        WHERE   UserID = @UserID     
                    </frame>
                </executionStack>
                <inputbuf>
                    Proc [Database Id = 6 Object Id = 855010127]    
                </inputbuf>
            </process>
        </process-list>

        <resource-list>
            <ridlock fileid="1" pageid="2392" dbid="6" objectname="mytable" id="lock164096b7800" mode="X" associatedObjectId="72057594051493888">
                <owner-list>
                    <owner id="process163feab3088" mode="X"/>
                </owner-list>
                <waiter-list>
                    <waiter id="process16409057468" mode="U" requestType="wait"/>
                </waiter-list>
            </ridlock>
            <ridlock fileid="1" pageid="2392" dbid="6" objectname="mytable" id="lock163f7fb2c80" mode="X" associatedObjectId="72057594051493888">
                <owner-list>
                    <owner id="process16409057468" mode="X"/>
                </owner-list>
                <waiter-list>
                    <waiter id="process163feab3088" mode="U" requestType="wait"/>
                </waiter-list>
            </ridlock>
        </resource-list>
    </deadlock>
</deadlock-list>

更新mytable
设置UserID=@tuserid
其中UserID=@UserID
Proc[数据库Id=6对象Id=855010127]
从mytable中删除
其中UserID=@UserID
Proc[数据库Id=6对象Id=855010127]

有人能解释一下死锁的原因吗

此时此刻，我很难理解这个X和U锁流

---

你能解释一下为什么X和U卡在死锁之间

您没有提供足够的查询详细信息，但是您共享的死锁图清楚地显示，由于并行性，这是一个的“writer-writer”死锁，因为所有授予或请求的锁都是X或U

<resource-list>
    <ridlock fileid="1" pageid="2392" dbid="6" objectname="xx" id="lock164096b7800" mode="X" associatedObjectId="72057594051493888">
        <owner-list>
            <owner id="process163feab3088" mode="X"/>
        </owner-list>
        <waiter-list>
            <waiter id="process16409057468" mode="U" requestType="wait"/>
        </waiter-list>
    </ridlock>
    <ridlock fileid="1" pageid="2392" dbid="6" objectname="mytable" id="lock163f7fb2c80" mode="X" associatedObjectId="72057594051493888">
        <owner-list>
            <owner id="process16409057468" mode="X"/>
        </owner-list>
        <waiter-list>
            <waiter id="process163feab3088" mode="U" requestType="wait"/>
        </waiter-list>
    </ridlock>
</resource-list>

这将在记录上获得必要的更新锁，并将停止其他进程以获取记录上的任何锁（共享/独占），并防止出现任何死锁

---

您还需要查找查询的顺序，错误的顺序可能导致循环死锁。在这种情况下，查询将等待不同事务中的另一个查询完成。

除了您的示例正在更新然后删除同一记录这一事实（这看起来是错误的）之外，您可以在执行DDL之前获得所有必需的XLock

select UserID
FROM mytable   with(xlock, holdlock, rowlock)
WHERE UserID  in (@ToUserID, @UserID)

UPDATE  mytable
SET     UserID = @ToUserID
WHERE   UserID = @UserID 

DELETE  FROM mytable
WHERE   UserID = @UserID 

---

我不认为用指定的UserId替换每一行有什么意义。因为，在更新之后，您尝试删除具有以前用户ID的每一行。这对我来说没有任何意义，删除查询将删除0行。你能解释一下最终的删除查询吗？请添加表中索引的详细信息。你的代码真的毫无意义。您可以发布真正的存储过程主体吗？

select UserID
FROM mytable   with(xlock, holdlock, rowlock)
WHERE UserID  in (@ToUserID, @UserID)

UPDATE  mytable
SET     UserID = @ToUserID
WHERE   UserID = @UserID 

DELETE  FROM mytable
WHERE   UserID = @UserID