昨天我只是将数据库附加到SQL2012，然后各个数据库都做了收缩事务日志的操作

兼容级别这些都没有改

再附加回SQL2005的时候就报错

在SQL2012里附加，确实是90级别，但是在SQL2005死活附加不上

备份数据库再还原也是一样

重建事务日志也是一样

然后我做了一个实验，检查一下附加到SQL2012的数据库和附加到SQL2005的数据库，两个数据库的文件头有什么不同

注意：两个数据库的兼容级别都是90，附加到SQL2012之后我也没有动过兼容级别！！

我们用同一个数据库，分别附加到SQL2005上和SQL2012上，看一下附加之后数据库的文件头有没有改变

这个数据库的兼容级别是90的

附加到SQL2012之后，我也不改变他的兼容级别

查看文件头的SQL语句如下，实际上就是数据库的第0页：

将结果复制粘贴到一个新建的记事本里，命名好

BUFFER:

BUF @0x035D7380
bpage = 0x05BC0000                   bhash = 0x00000000                   bpageno = (1:0)
bdbid = 5                            breferences = 0                      bUse1 = 8142
bstat = 0xc00009                     blog = 0x59ca2159                    bnext = 0x00000000
PAGE HEADER:

Page @0x05BC0000
m_pageId = (1:0)                     m_headerVersion = 1                  m_type = 15
m_typeFlagBits = 0x0                 m_level = 0                          m_flagBits = 0x208
m_objId (AllocUnitId.idObj) = 99     m_indexId (AllocUnitId.idInd) = 0    Metadata: AllocUnitId = 6488064
Metadata: PartitionId = 0            Metadata: IndexId = 0                Metadata: ObjectId = 99
m_prevPage = (0:0)                   m_nextPage = (0:0)                   pminlen = 0
m_slotCnt = 1                        m_freeCnt = 7636                     m_freeData = 2844
m_reservedCnt = 0                    m_lsn = (132:328:1)                  m_xactReserved = 0
m_xdesId = (0:0)                     m_ghostRecCnt = 0                    m_tornBits = 1431739479
Allocation Status
GAM (1:2) = ALLOCATED                SGAM (1:3) = NOT ALLOCATED           PFS (1:1) = 0x44 ALLOCATED 100_PCT_FULL
DIFF (1:6) = CHANGED                 ML (1:7) = NOT MIN_LOGGED           
File Header Data:
Record Type = PRIMARY_RECORD         Record Attributes =  NULL_BITMAP VARIABLE_COLUMNS
Memory Dump @0x5D95C952
00000000:   30000800 00000000 2d000000 00000000 ?0.......-.......        
00000010:   2c007a00 7a007c00 7e008200 86008a00 ?,.z.z.|.~.......        
00000020:   8e009800 a200ac00 ac00b000 b400b800 ?................        
00000030:   bc00c600 e200ec00 f6000001 10011a01 ?................        
00000040:   2a012e01 38013801 44015401 54015401 ?*...8.8.D.T.T.T.        
00000050:   54015401 54015401 64016401 64016e01 ?T.T.T.T.d.d.d.n.        
00000060:   78019401 9e01ae01 ca019eb2 1d7874c9 ?x............xt.        
00000070:   5d4d85b9 d1422e77 c1620100 01008002 ?]M...B.w.b......        
00000080:   0000ffff ffff8000 00000000 00000000 ?................        
00000090:   00000000 00000000 00000000 00000000 ?................        
000000A0:   00000000 00000000 00000000 80010000 ?................        
000000B0:   00000000 ffffffff 00020000 7e000000 ?............~...        
000000C0:   c6000000 01007e00 0000c600 00000100 ?......~.........        
000000D0:   0000355a f94bc493 9149ac29 044140d0 ?..5Z.K...I.).A@.        
000000E0:   3b1f7e00 0000b100 00002500 00000000 ?;.~.......%.....        
000000F0:   00000000 00008400 00003601 00002500 ?..........6...%.        
00000100:   0567c9fb b5520346 853c86ad b3f47661 ?.g...R.F.<....va        
00000110:   00000000 00000000 0000018e a4cb618f ?..............a.        
00000120:   414c90c3 68f1a4fd 0d810800 00007e00 ?AL..h.........~.        
00000130:   0000c600 00000100 44004c00 47005000 ?........D.L.G.P.        
00000140:   4f005300 cf6c06e9 4b9b3649 a11c2b70 ?O.S..l..K.6I..+p        
00000150:   dbebb977 355af94b c4939149 ac290441 ?...w5Z.K...I.).A        
00000160:   40d03b1f 00000000 00000000 00000000 ?@.;.............        
00000170:   00000000 00000000 00000000 00000000 ?................        
00000180:   00000000 00000000 00000000 00000000 ?................        
00000190:   00000000 7e000000 b1000000 25003804 ?....~.......%.8.        
000001A0:   48829a28 104c95f3 4b9d6a91 ab480000 ?H..(.L..K.j..H..        
000001B0:   00000000 00000000 00000000 00000000 ?................        
000001C0:   00000000 00000000 0000???????????????..........              
BindingID = 781db29e-c974-4d5d-85b9-d1422e77c162                          FileGroupId = 1
FileIdProp = 1                       Size = 640                           MaxSize = 65535
Growth = 128                         Perf = 0                             BackupLsn = (0:0:0)
MaxLsn = (126:198:1)                 FirstLsn = (126:177:37)              OldestRestoredLsn = (0:0:0)
FirstUpdateLsn = (0:0:0)             FirstNonloggedUpdateLsn = [NULL]     CreateLsn = (0:0:0)
DifferentialBaseLsn = (132:310:37)   DifferentialBaseGuid = fbc96705-52b5-4603-853c-86adb3f47661
MinSize = 384                        Status = 0                           UserShrinkSize = 65535

DBCC 执行完毕。如果 DBCC 输出了错误信息，请与系统管理员联系。