[摘自 水木清华站] * S% \$ z+ T$ [4 r, C) s7 e! ]% Q) J ; d% Z }8 t, ?* d+ E2 W; }( o 4 x0 _9 n8 M0 a+ U% @
对于SQL中的TEXT、IMAGE、MEMO字段的存取,可以采用下列程序: + m2 _' ]# s6 X( n! W8 `% ~+ \& _+ X
BLOB字段的读取: , p, }" O7 n. w. ?, k4 Y TBlobSTream* TemplateStream; 3 l, G: G+ ]7 Z: J0 W char* TempPlatePtr; * H% B; [; ~! w X5 I9 s0 D
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TemplateStream=new TBlobStream((TBlobField*)WebQuery->FieldByName $ m$ d+ z8 @) f7 X
("SearchTem"),bmReadWrite); ' K$ `9 @0 Z& `, y$ I
TemplatePtr= new char[TemplateStream->Size]; $ x5 O. ^" K) i; a
TemplateStream->Read(TemplatePtr, TemplateStream->Size); 6 j \ |9 l( g # { Z, O( K' q* w- M
BLOB字段的写入: f5 I G: r% T+ ? TBlobSTream* TemplateStream; 1 `' ], H# y ~- l char* TempPlatePtr; + \# i1 _# M4 B6 p* L+ H, E) Z% u & P/ h6 I( w1 x) {# d9 E. L
TemplateStream=new TBlobStream((TBlobField*)WebQuery->FieldByName C( F! o5 ~5 T9 T ("SearchTem"),bmReadWrite); ' ^( i6 z( [! G$ n4 L
TemplatePtr= new char[TemplateStream->Size]; 8 d% b8 r. O6 G3 a
TemplateStream->Write(TemplatePtr, TemplateStream->Size); 5 U0 F2 |9 U5 u3 f : Z5 Z/ o+ z9 a: l, h/ \: g/ o________________________________________________________________ 8 C( ~ L( C4 U* c
补充: 7 m1 B) ~, N0 M X" j9 D获得字段的大小用函数datalength 7 _8 ~# C6 s) N Q8 |8 u
; a0 {8 o0 J+ N6 _& S# E2 x6 B' Z, mSQL Server端要作一点设置: 1 b9 v( G+ Q9 i8 IBy default, WRITETEXT is a nonlogged operation. This means that 7 [( u. c( }) j. ftext or image data is not logged when it is written into the database. / n' V# a1 D9 J4 i) wTo use WRITETEXT in its default, nonlogged state, : ]* @3 z+ r- e+ m$ K l//注意!! , q& r- Z0 P; A! }1 o) v& D* c* Q
the system administrator must use the sp_dboption system stored ( s& e* S1 l" f" N8 A. R5 s( Q& @procedure to set select into/bulkcopy, & c8 G- y2 N% b) S) F
// + |* n( H1 ^' ]* @/ ]* Uwhich allows nonlogged data to be inserted. 6 z& u! Q9 y% t% ?
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做了试验,直接写SQL语句好象不行. _* o! Z2 ]3 x____________________________________________________________________ 3 y7 v3 E% S# O6 g7 J5 V
一些注意事项和一个例子 / o4 J. R" ?5 K4 }2 X" u i
在写入时: " [4 c1 D) E% ]1 t1 g& t(1)如果使用的是TTable,则要将其ReadOnly属性先置为false,然后调用Edit函数; 8 h9 w5 \3 K1 M2 Y2 g O(2)如果使用的是TQuery,则要将其RequestLive属性先置为true,然后调用Edit函数; , `: f! b/ H" k5 [
使得TTable(TQuery)是可写的. 1 q6 R, w; R( v& \
# M* r" [/ g; |7 n% c3 ^3 u0 y下面是一个使用TQuery往content表(主键file_id)中插入一条记录的例子, 8 f9 M: o) f$ |1 j. n4 F# P. Y
script为一个BLOB字段: 8 d) u! ?7 C$ Y3 f6 J' G TBlobStream *pScriptStream; ; M% s' u* t4 y6 C8 ], Q //插入一条记录 : m, U* r' i% h" Y( V9 P strSQL1="insert into content(file_id,script,key_image) values('"; . Q3 {, b1 [0 W4 r7 i) q" n; f strSQL1=strSQL1+m_szFileID+"',null,null)"; 8 g( m4 c) h$ j
dmStoryEditor->qryExec->SQL->Clear(); 3 e( V0 A; @' ^8 q
dmStoryEditor->qryExec->SQL->Add(strSQL1); 0 ?3 a9 B7 L! R2 W [ dmStoryEditor->qryExec->ExecSQL(); ( T$ y1 h9 M8 t9 p dmStoryEditor->qryExec->Close(); 9 }+ g) U( A+ h8 J" }( Z //整理要写入的Blob数据 4 B! e+ Y( T; n* n1 X3 S
LockMemories(NewsScript); ; ]5 L/ w7 _6 W& u E NewsScript.GetEdition(NewsScript.m_ScriptHead.byteEditionNum); ) ?) O: Z* O* t NewsScript.m_pScript=(BYTE *)GlobalLock(NewsScript.m_hScript); 9 H6 X1 b n# v/ D" S: t5 F
if(NewsScript.m_pScript!=NULL) - ^, E) g8 z* i/ r; u; o
{ % Y+ e i$ m+ y& j0 H1 L //再将刚插入的记录读出来,使该Query与该条记录关联 5 P2 l, Q1 x8 n0 v
strSQL1="select file_id,script from content where file_id='"+ 6 m8 G, V% S3 y4 ]8 O
m_szFileID+"'"; |8 i. c# ~) L0 Y1 u# _
//允许该Query写 9 X; `- v$ S* Y& X' S5 g
dmStoryEditor->qryExec->RequestLive=true; 9 D; H" Q+ t2 ]* J: ` dmStoryEditor->qryExec->SQL->Clear(); * W* N7 `7 @4 x3 T( Y; S, d8 \ dmStoryEditor->qryExec->SQL->Add(strSQL1); 5 x8 b9 l: ^. r9 `$ b6 i* w
dmStoryEditor->qryExec->Open(); 4 d* y( x6 {: J3 x% j3 M dmStoryEditor->qryExec->First(); $ s: G2 \1 G( ~6 ^! R/ P
//将该Query置为可写 7 g( ^3 W! {+ g% X1 [ D
dmStoryEditor->qryExec->Edit(); 8 K, ?5 I0 `; Z pScriptStream=new TBlobStream((TBlobField*)dmStoryEditor-> 1 y2 d1 F7 @- b! R; ^7 e5 \ qryExec->FieldByName("script"),bmReadWrite); ! } c, ~7 y3 e. R% s6 g* L
pScriptStream->Write(NewsScript.m_pScript, % A: u4 ] y" y; |. s4 z7 u% ]7 e
NewsScript.m_lScriptRealSize); 4 q/ v( v# l% z9 x. p
dmStoryEditor->qryExec->ost(); 9 z) |7 Y& T. ^7 a y
dmStoryEditor->qryExec->RequestLive=false; 0 |/ i( ?" a( q1 P3 w+ H delete pScriptStream; ] K5 |- a4 {. t } ; }" D7 l9 j/ d( _
GlobalUnlock(NewsScript.m_hScript); & N2 J7 \2 P* Z' z4 q7 r
UnLockMemories(NewsScript);