我有一张桌子，其中包含一起购买的物品对和配对发生的次数。
item_1 item_2 count
123 234 5
345 567 22
567 345 22
890 345 6
有些配对只是顺序不同（即第2行和第3行）。
有没有一种简单的方法可以减少这张桌子的费用？
答案 0 :(得分：0)
您可以对一对相同的分类进行分类，并将其与两者中最小和最大的相比较。并选择其中一个。
select item_1,item_2,count
from (select t.*
,row_number() over(partition by case when item_1<item_2 then item_1 else item_2 end,
case when item_1>item_2 then item_1 else item_2 end,
count
order by item_1) as rnum
from tbl t
) t
where rnum=1
编辑：根据戈登的评论，如果只有当计数相同时必须删除重复项，请使用
Process: Drum Hero [66758]
Path: /Volumes/VOLUME/*/Drum Hero.app/Contents/MacOS/Drum Hero
Identifier: MF.Drum-Hero
Version: 1.0 (1)
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: Drum Hero [66758]
User ID: 1682957694
Date/Time: 2017-09-13 10:33:16.940 -0400
OS Version: Mac OS X 10.12.6 (16G29)
Report Version: 12
Anonymous UUID: B0637F3C-A9B3-E010-DB95-C3584B6B7A8F
Time Awake Since Boot: 1100000 seconds
System Integrity Protection: enabled
Notes: Translocated Process
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00007fef6bbffff8
Exception Note: EXC_CORPSE_NOTIFY
Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [0]
VM Regions Near 0x7fef6bbffff8:
Stack 0000700002a04000-0000700002a86000 [ 520K] rw-/rwx SM=COW thread 8
-->
MALLOC_TINY 00007fef6bc00000-00007fef6c000000 [ 4096K] rw-/rwx SM=PRV
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_platform.dylib 0x00007fffe6b421c6 _platform_memmove$VARIANT$Nehalem + 486
1 com.apple.SpriteKit 0x00007fffd781c405 std::__1::vector<SKCNode*, std::__1::allocator<SKCNode*> >::insert(std::__1::__wrap_iter<SKCNode* const*>, SKCNode* const&) + 131
2 com.apple.SpriteKit 0x00007fffd781c326 SKCNode::insertChildAtIndex(SKCNode*, int) + 294
3 com.apple.SpriteKit 0x00007fffd784ffd2 -[SKNode insertChild:atIndex:] + 294
4 com.apple.SpriteKit 0x00007fffd784fe8b -[SKNode addChild:] + 68
5 MF.Drum-Hero 0x0000000105769cb9 0x105761000 + 36025
6 MF.Drum-Hero 0x0000000105769a48 0x105761000 + 35400
7 MF.Drum-Hero 0x0000000105769685 0x105761000 + 34437
8 MF.Drum-Hero 0x0000000105776724 0x105761000 + 87844
9 com.apple.GameplayKit 0x00007fffd2a9975e -[GKStateMachine updateWithDeltaTime:] + 62
10 MF.Drum-Hero 0x000000010576ce44 0x105761000 + 48708
11 com.apple.SpriteKit 0x00007fffd7823dd6 -[SKScene _update:] + 365
12 com.apple.SpriteKit 0x00007fffd77cee6a -[SKView _update:] + 1156
13 com.apple.SpriteKit 0x00007fffd77cb920 __51-[SKView _vsyncRenderForTime:preRender:postRender:]_block_invoke.385 + 285
14 com.apple.SpriteKit 0x00007fffd77cad17 -[SKView _vsyncRenderForTime:preRender:postRender:] + 658
15 com.apple.SpriteKit 0x00007fffd77ccc8e __29-[SKView setUpRenderCallback]_block_invoke + 291
16 com.apple.SpriteKit 0x00007fffd784783f -[SKDisplayLink _callbackForNextFrame:] + 324
17 com.apple.SpriteKit 0x00007fffd7847a42 ___Z22_cvDisplayLinkCallbackP15__CVDisplayLinkPK11CVTimeStampS3_yPyPv_block_invoke + 36
18 libdispatch.dylib 0x00007fffe6906524 _dispatch_call_block_and_release + 12
19 libdispatch.dylib 0x00007fffe68fd8fc _dispatch_client_callout + 8
20 libdispatch.dylib 0x00007fffe690aaac _dispatch_main_queue_callback_4CF + 925
21 com.apple.CoreFoundation 0x00007fffd0c3fd69 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
22 com.apple.CoreFoundation 0x00007fffd0c0104d __CFRunLoopRun + 2221
23 com.apple.CoreFoundation 0x00007fffd0c00544 CFRunLoopRunSpecific + 420
24 com.apple.HIToolbox 0x00007fffd015febc RunCurrentEventLoopInMode + 240
25 com.apple.HIToolbox 0x00007fffd015fcf1 ReceiveNextEventCommon + 432
26 com.apple.HIToolbox 0x00007fffd015fb26 _BlockUntilNextEventMatchingListInModeWithFilter + 71
27 com.apple.AppKit 0x00007fffce6f8a54 _DPSNextEvent + 1120
28 com.apple.AppKit 0x00007fffcee747ee -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 2796
29 com.apple.AppKit 0x00007fffce6ed3db -[NSApplication run] + 926
30 com.apple.AppKit 0x00007fffce6b7e0e NSApplicationMain + 1237
31 libdyld.dylib 0x00007fffe6933235 start + 1
Thread 1:: CVDisplayLink
0 libsystem_kernel.dylib 0x00007fffe6a61bf2 __psynch_cvwait + 10
1 libsystem_pthread.dylib 0x00007fffe6b4d833 _pthread_cond_wait + 769
2 com.apple.CoreVideo 0x00007fffd22da977 CVDisplayLink::waitUntil(unsigned long long) + 233
3 com.apple.CoreVideo 0x00007fffd22da762 CVDisplayLink::runIOThread() + 520
4 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
5 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
6 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 2:: com.apple.NSEventThread
0 libsystem_kernel.dylib 0x00007fffe6a5a34a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fffe6a59797 mach_msg + 55
2 com.apple.CoreFoundation 0x00007fffd0c01874 __CFRunLoopServiceMachPort + 212
3 com.apple.CoreFoundation 0x00007fffd0c00cf1 __CFRunLoopRun + 1361
4 com.apple.CoreFoundation 0x00007fffd0c00544 CFRunLoopRunSpecific + 420
5 com.apple.AppKit 0x00007fffce845f02 _NSEventThread + 205
6 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
7 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
8 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 3:
0 libsystem_kernel.dylib 0x00007fffe6a6244e __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffe6b4c621 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffe6b4c07d start_wqthread + 13
Thread 4:
0 libobjc.A.dylib 0x00007fffe6042cdb search_method_list(method_list_t const*, objc_selector*) + 107
1 libobjc.A.dylib 0x00007fffe60450a5 lookUpImpOrForward + 383
2 libobjc.A.dylib 0x00007fffe6044a94 _objc_msgSend_uncached + 68
3 com.apple.Foundation 0x00007fffd2615716 +[NSConcreteNotification newTempNotificationWithName:object:userInfo:] + 123
4 com.apple.Foundation 0x00007fffd261565f -[NSNotificationCenter postNotificationName:object:userInfo:] + 42
5 MF.Drum-Hero 0x000000010576a413 0x105761000 + 37907
6 com.apple.CoreFoundation 0x00007fffd0c1654c __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
7 com.apple.CoreFoundation 0x00007fffd0c1644b _CFXRegistrationPost + 427
8 com.apple.CoreFoundation 0x00007fffd0c161b2 ___CFXNotificationPost_block_invoke + 50
9 com.apple.CoreFoundation 0x00007fffd0bd4782 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 2018
10 com.apple.CoreFoundation 0x00007fffd0bd376b _CFXNotificationPost + 667
11 com.apple.Foundation 0x00007fffd2615677 -[NSNotificationCenter postNotificationName:object:userInfo:] + 66
12 MF.Drum-Hero 0x000000010576df60 0x105761000 + 53088
13 MF.Drum-Hero 0x000000010576de5f 0x105761000 + 52831
14 MF.Drum-Hero 0x000000010576dd34 0x105761000 + 52532
15 com.apple.audio.midi.CoreMIDI 0x00000001057b6d5e LocalMIDIReceiverList::HandleMIDIIn(unsigned int, unsigned int, void*, MIDIPacketList const*) + 120
16 com.apple.audio.midi.CoreMIDI 0x00000001057b6c12 MIDIProcess::RunMIDIInThread() + 210
17 com.apple.audio.midi.CoreMIDI 0x00000001057c3a9a XThread::RunHelper(void*) + 10
18 com.apple.audio.midi.CoreMIDI 0x00000001057c7053 CAPThread::Entry(CAPThread*) + 85
19 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
20 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
21 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 5:: com.apple.coreaudio.AQClient
0 libsystem_kernel.dylib 0x00007fffe6a5a34a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fffe6a59797 mach_msg + 55
2 com.apple.CoreFoundation 0x00007fffd0c01874 __CFRunLoopServiceMachPort + 212
3 com.apple.CoreFoundation 0x00007fffd0c00cf1 __CFRunLoopRun + 1361
4 com.apple.CoreFoundation 0x00007fffd0c00544 CFRunLoopRunSpecific + 420
5 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9d1899 GenericRunLoopThread::Entry(void*) + 189
6 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9d172b CAPThread::Entry(CAPThread*) + 85
7 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
8 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
9 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 6:: AQConverterThread
0 libsystem_kernel.dylib 0x00007fffe6a61bf2 __psynch_cvwait + 10
1 libsystem_pthread.dylib 0x00007fffe6b4d7fa _pthread_cond_wait + 712
2 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9ff256 CAGuard::Wait() + 52
3 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9f9f0d AQConverterManager::AQConverterThread::Run() + 707
4 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9f9c3f AQConverterManager::AQConverterThread::ConverterThreadEntry(void*) + 9
5 com.apple.audio.toolbox.AudioToolbox 0x00007fffcf9d172b CAPThread::Entry(CAPThread*) + 85
6 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
7 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
8 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 7:: AudioStreamerImpl::sIOWorkerProcess
0 libsystem_kernel.dylib 0x00007fffe6a5a386 semaphore_wait_trap + 10
1 libdispatch.dylib 0x00007fffe6915a77 _os_semaphore_wait + 16
2 libdispatch.dylib 0x00007fffe6906891 _dispatch_semaphore_wait_slow + 103
3 com.apple.audio.units.Components 0x0000000105e8ce25 CASemaphore::Wait() + 23
4 com.apple.audio.units.Components 0x0000000105e8b94f AudioStreamerImpl::sIOWorkerProcess(void*) + 735
5 com.apple.audio.units.Components 0x0000000105ed16e5 CAPThread::Entry(CAPThread*) + 85
6 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
7 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
8 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 8:: com.apple.audio.IOThread.client
0 libsystem_kernel.dylib 0x00007fffe6a5a34a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fffe6a59797 mach_msg + 55
2 com.apple.audio.CoreAudio 0x00007fffd0769935 HALB_MachPort::SendMessageWithReply(unsigned int, unsigned int, unsigned int, unsigned int, mach_msg_header_t*, bool, unsigned int) + 127
3 com.apple.audio.CoreAudio 0x00007fffd07698a6 HALB_MachPort::SendSimpleMessageWithSimpleReply(unsigned int, unsigned int, int, int&, bool, unsigned int) + 42
4 com.apple.audio.CoreAudio 0x00007fffd07668d0 HALC_ProxyIOContext::IOWorkLoop() + 1196
5 com.apple.audio.CoreAudio 0x00007fffd0766264 HALC_ProxyIOContext::IOThreadEntry(void*) + 128
6 com.apple.audio.CoreAudio 0x00007fffd0765fa3 HALB_IOThread::Entry(void*) + 75
7 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
8 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
9 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 9:
0 libsystem_kernel.dylib 0x00007fffe6a6244e __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffe6b4c48e _pthread_wqthread + 1023
2 libsystem_pthread.dylib 0x00007fffe6b4c07d start_wqthread + 13
Thread 10:
0 libsystem_pthread.dylib 0x00007fffe6b4c070 start_wqthread + 0
1 ??? 0x0000700002771ad0 0 + 123145343670992
Thread 11:: com.apple.audio.IOThread.client
0 libsystem_kernel.dylib 0x00007fffe6a5a34a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fffe6a59797 mach_msg + 55
2 com.apple.audio.CoreAudio 0x00007fffd0769935 HALB_MachPort::SendMessageWithReply(unsigned int, unsigned int, unsigned int, unsigned int, mach_msg_header_t*, bool, unsigned int) + 127
3 com.apple.audio.CoreAudio 0x00007fffd07698a6 HALB_MachPort::SendSimpleMessageWithSimpleReply(unsigned int, unsigned int, int, int&, bool, unsigned int) + 42
4 com.apple.audio.CoreAudio 0x00007fffd07668d0 HALC_ProxyIOContext::IOWorkLoop() + 1196
5 com.apple.audio.CoreAudio 0x00007fffd0766264 HALC_ProxyIOContext::IOThreadEntry(void*) + 128
6 com.apple.audio.CoreAudio 0x00007fffd0765fa3 HALB_IOThread::Entry(void*) + 75
7 libsystem_pthread.dylib 0x00007fffe6b4c93b _pthread_body + 180
8 libsystem_pthread.dylib 0x00007fffe6b4c887 _pthread_start + 286
9 libsystem_pthread.dylib 0x00007fffe6b4c08d thread_start + 13
Thread 0 crashed with X86 Thread State (64-bit):
rax: 0x00007fef6bd94fd8 rbx: 0x00007fef6bd94fd8 rcx: 0x0000000000000008 rdx: 0xffffffffffe6b028
rdi: 0x00007fef6bc00040 rsi: 0x00007fef6bc00038 rbp: 0x00007fff5a49c860 rsp: 0x00007fff5a49c860
r8: 0x0000000000000040 r9: 0x00007fffec5954f0 r10: 0x00007fffecee1b60 r11: 0x00007fef6bd94fc8
r12: 0x00007fef720cd3e8 r13: 0x00007fef6bd95090 r14: 0x00007fef6bd94fd0 r15: 0x00007fff5a49c8f0
rip: 0x00007fffe6b421c6 rfl: 0x0000000000010202 cr2: 0x00007fef6bbffff8
Logical CPU: 2
Error Code: 0x00000004
Trap Number: 14
答案 1 :(得分：0)
如果＆＃34; dups＆＃34;只能在任一方向出现一次，那么方便的方法是：
select t.*
from t
where t.item_1 <= t.item_2
union all
select t.*
from t t
where t.item_1 > t.item2 and
not exists (select 1
from t t2
where t2.item_1 = t.item_2 and t.item_2 = t.item_1 and t2.count = t.count
);
答案 2 :(得分：0)
您可以使用此脚本。
DECLARE @T TABLE (item_1 INT, item_2 INT , [count] INT)
INSERT INTO @T
VALUES
(123 ,234, 5),
(345 ,567, 22),
(567 ,345, 22),
(890 ,345, 6)
;WITH BASE AS
(
SELECT RN = ROW_NUMBER() OVER(ORDER BY item_1), * FROM @T
)
SELECT T1.item_1, T1.item_2, T1.count FROM BASE T1
OUTER APPLY (SELECT TOP 1 *
FROM BASE T2
WHERE T2.RN > T1.RN AND T1.item_1 = T2.item_2 AND T1.item_2 = T2.item_1) X
WHERE X.RN IS NULL
结果
item_1 item_2 count
----------- ----------- -----------
123 234 5
567 345 22
890 345 6