怎样用ADO打开一个带密码的Access库？

韩冰

<>  </P>
, U# Y5 t7 v3 ^/ C  M8 ]<>Creates a new Recordset object and appends it to the Recordsets collection. </P>
9 g# z7 T) P: T) \- d: ?<>  </P>
<>Syntax </P>
2 {" K, O& |7 g, h9 j<>  </P>
: x) b" L* Y" {% Q; A' ?- s& b0 D, x<>For Connection and Database objects: </P>
5 v; f$ a7 j) W<>  </P>
<>Set recordset = object.OpenRecordset (source, type, options, lockedits) </P>
* E0 I* L% W; }' w& j<>  </P>
<>For QueryDef, Recordset, and TableDef objects: </P>
<>  </P>
- Y  g. M( O6 w+ O<>Set recordset = object.OpenRecordset (type, options, lockedits) </P>
. [: Z2 k/ {) z1 T4 h$ ^  _" i<>  </P>
<>The OpenRecordset method syntax has these parts. </P>
, G  b3 m; r0 {. q# \' q$ H<>  </P>
$ t4 h/ r9 \2 g<>art    Description </P>
! Q5 F- I' A2 w8 m2 F<>recordset       An object variable that represents the Recordset object you wantt to </P>
<>open. </P>
$ x/ J' t) Y( ?5 x  J; n<>object  An object variable that represents an existing object from which you </P>
<>want to create the new Recordset. </P>
  H& o4 r8 T# u: `* B5 M<>source  A String specifying the source of the records for the new Recordset. </P>
<>The source can be a table name, a query name, or an SQL statement that </P>
<>returns records. For table-type Recordset objects in Microsoft Jet databases, </P>
<>the source can only be a table name. </P>
<>type    Optional. A constant that indicates the type of Recordset to open, as </P>
<>specified in Settings. </P>
<>options Optional. A combination of constants that specify characteristics of </P>
<>the new Recordset, as listed in Settings. </P>
<>lockedits       Optional. A constant that determines the locking for the Recordsset, </P>
3 C: [1 L( ?+ n, k" d4 p<P>as specified in Settings. </P>
<P>Settings </P>
<P>  </P>
<P>You can use one of the following constants for the type argument. </P>
<P>  </P>
<P>Constant        Description </P>
<P>  </P>
& ~7 V! `, R. u) ^5 `7 T<P>  </P>
<P>dbOpenTable     Opens a table-type Recordset object (Microsoft Jet workspaces </P>
( C2 N% T* `( J' }<P>only). </P>
5 i5 K! n! V6 I1 F- p6 @0 ]" ?2 `6 u<P>dbOpenDynamic   Opens a dynamic-type Recordset object, which is similar to an </P>
<P>ODBC dynamic cursor. (ODBCDirect workspaces only) </P>
' J6 T0 o& j* q' ]" D" g7 p<P>dbOpenDynaset   Opens a dynaset-type Recordset object, which is similar to an </P>
<P>ODBC keyset cursor. </P>
<P>dbOpenSnapshot  Opens a snapshot-type Recordset object, which is similar to an </P>
<P>ODBC static cursor. </P>
, g4 C7 c5 f( d; }" q<P>dbOpenForwardOnly?Opens a forward-only-type Recordset object. </P>
<P>Note   If you open a Recordset in a Microsoft Jet workspace and you don't </P>
<P>specify a type, OpenRecordset creates a table-type Recordset, if possible. If </P>
0 ~! q8 W: g9 m  N  R9 ?<P>you specify a linked table or query, OpenRecordset creates a dynaset-type </P>
<P>Recordset. In an ODBCDirect workspace, the default setting is dbOpenForwardOnl </P>
<P>y. </P>
2 b) u! E8 ?8 F* f0 e" L<P>  </P>
# _- T2 A; i$ c2 Y" T2 N<P>You can use a combination of the following constants for the options </P>
! J; d) C1 _9 I+ U0 _$ i1 o<P>argument. </P>
<P>  </P>
9 ^5 X4 \, `( g0 u# H/ y9 X<P>Constant        Description </P>
' E; }3 H/ u& P- O8 d<P>dbAppendOnly?Allows users to append new records to the Recordset, but </P>
<P>prevents them from editing or deleting existing records (Microsoft Jet </P>
0 f9 M* g: u% }  I. X<P>dynaset-type Recordset only). </P>
) E5 I; [2 o6 ?/ [# V<P>dbSQLPassThrough?Passes an SQL statement to a Microsoft Jet-connected ODBC </P>
/ S' g6 h5 ?  Q& W, Y<P>data source for processing (Microsoft Jet snapshot-type Recordset only). </P>
! X# {% _' c7 D7 V1 X<P>dbSeeChanges    Generates a run-time error if one user is changing data that </P>
0 |( |" _+ R, J$ s2 c& T( n% q; ^<P>another user is editing (Microsoft Jet dynaset-type Recordset only). This is </P>
; X$ p% Z. N% P; M$ w<P>useful in applications where multiple users have simultaneous read/write </P>
<P>access to the same data. </P>
' U, \6 w* M. [5 t4 E2 ?0 l) j" G<P>dbDenyWrite?Prevents other users from modifying or adding records (Microsoft </P>
<P>Jet Recordset objects only). </P>
<P>dbDenyRead?Prevents other users from reading data in a table (Microsoft Jet </P>
<P>table-type Recordset only). </P>
<P>dbForwardOnly?Creates a forward-only Recordset (Microsoft Jet snapshot-type </P>
: l) \" m3 |5 Z9 [<P>Recordset only). It is provided only for backward compatibility, and you </P>
- f$ A; _+ T4 C- a- v<P>should use the dbOpenForwardOnly constant in the type argument instead of </P>
<P>using this option. </P>
<P>dbReadOnly?Prevents users from making changes to the Recordset (Microsoft Jet </P>
6 @1 p7 D8 K) j2 v9 N8 ^<P>only). The dbReadOnly constant in the lockedits argument replaces this </P>
, y/ B* }: [, F: I5 Z8 D5 k<P>option, which is provided only for backward compatibility. </P>
<P>dbRunAsync      Runs an asynchronous query (ODBCDirect workspaces only). </P>
6 R9 r; ?" V7 J! N8 P<P>dbExecDirect?Runs a query by skipping SQLPrepare and directly calling </P>
) L! F3 H  \/ r% A( c<P>SQLExecDirect (ODBCDirect workspaces only). Use this option only when you抮e </P>
<P>not opening a Recordset based on a parameter query. For more information, see </P>
0 ], W# a) P* w  m<P>the "Microsoft ODBC 3.0 Programmer抯 Reference." </P>
<P>dbInconsistent?Allows inconsistent updates (Microsoft Jet dynaset-type and </P>
) ^' u5 V) ]8 M7 {' l6 w6 |' g. s<P>snapshot-type Recordset objects only). </P>
: }2 u5 F- N' \2 ^, A<P>dbConsistent?Allows only consistent updates (Microsoft Jet dynaset-type and </P>
; m% [3 J3 b4 G0 `' Y<P>snapshot-type Recordset objects only). </P>
<P>Note   The constants dbConsistent and dbInconsistent are mutually exclusive, </P>
<P>and using both causes an error. Supplying a lockedits argument when options </P>
<P>uses the dbReadOnly constant also causes an error. </P>
<P>  </P>
+ O! T2 w" y' D) ^; l* g<P>You can use the following constants for the lockedits argument. </P>
<P>  </P>
<P>Constant        Description </P>
<P>dbReadOnly      Prevents users from making changes to the Recordset (default for </P>
<P>ODBCDirect workspaces). You can use dbReadOnly in either the options argument </P>
<P>or the lockedits argument, but not both. If you use it for both arguments, a </P>
" c. `8 \0 c. I& t" ^<P>run-time error occurs. </P>
+ k' z1 P+ z- L6 X+ y. f9 E<P>dbPessimistic?Uses pessimistic locking to determine how changes are made to </P>
<P>the Recordset in a multiuser environment. The page containing the record </P>
  w) n9 `( d! s, l<P>you're editing is locked as soon as you use the Edit method (default for </P>
<P>Microsoft Jet workspaces). </P>
7 }% E8 l! J$ c3 u% _<P>dbOptimistic?Uses optimistic locking to determine how changes are made to the </P>
- C! T9 m9 [7 Z# k: o' B<P>Recordset in a multiuser environment. The page containing the record is not </P>
; F9 C4 M' y5 H: d  W<P>locked until the Update method is executed. </P>
$ K( O9 r& q+ K" _, V: y' o<P>dbOptimisticValue?Uses optimistic concurrency based on row values (ODBCDirect </P>
<P>workspaces only). </P>
+ X1 O) {+ h; U, l<P>dbOptimisticBatch?Enables batch optimistic updating (ODBCDirect workspaces </P>
<P>only). </P>
+ m5 G1 i. c( n1 I( {9 P  B3 I<P>Remarks </P>
<P>  </P>
0 U. k! ^! w8 u3 Q<P>In a Microsoft Jet workspace, if object refers to a QueryDef object, or a </P>
<P>dynaset- or snapshot-type Recordset, or if source refers to an SQL statement </P>
% ?  `8 h5 H1 z( [8 l9 N<P>or a TableDef that represents a linked table, you can't use dbOpenTable for </P>
% T( B( u( t( U* E! i9 F<P>the type argument; if you do, a run-time error occurs. If you want to use an </P>
<P>SQL pass-through query on a linked table in a Microsoft Jet-connected ODBC </P>
. @! a# x. \2 H<P>data source, you must first set the Connect property of the linked table's </P>
<P>database to a valid ODBC connection string. If you only need to make a single </P>
<P>pass through a Recordset opened from a Microsoft Jet-connected ODBC data </P>
. H# j7 J& I/ C' V" a$ t<P>source, you can improve performance by using dbOpenForwardOnly for the type </P>
* F: q# R  K8 z- q) i/ Q<P>argument. </P>
<P>  </P>
<P>If object refers to a dynaset- or snapshot-type Recordset, the new Recordset </P>
<P>is of the same type object. If object </P>
<P> refers to a table-type Recordset object, the type of the new object is a </P>
- r  f. E$ M% n, E, F9 V<P>dynaset-type Recordset. You can't open new Recordset objects from forward-only </P>
9 m* J: _) [+ y8 j9 m9 C3 `<P>杢ype or ODBCDirect Recordset objects. </P>
<P>In an ODBCDirect workspace, you can open a Recordset containing more than one </P>
<P>select query in the source argument, such as </P>
<P>  </P>
6 q2 S, ?3 T# _4 w* y( I4 E3 ^- T<P>"SELECT LastName, FirstName FROM Authors </P>
* |  \' V: I5 f, G( A6 l<P>WHERE LastName = 'Smith'; </P>
<P>SELECT Title, ISBN FROM Titles </P>
<P>WHERE ISBN Like '1-55615-*'" </P>
4 d* u. k5 z, F: H<P>  </P>
) o- f1 x: M3 S& Q<P>The returned Recordset will open with the results of the first query. To </P>
( l* I9 H: ^+ C) B1 _4 G<P>obtain the result sets of records from subsequent queries, use the </P>
# _# G% q) L7 n" e" F<P>NextRecordset method. </P>
: y& r% X7 s' t<P>  </P>
<P>Note   You can send DAO queries to a variety of different database servers </P>
<P>with ODBCDirect, and different servers will recognize slightly different </P>
<P>dialects of SQL. Therefore, context-sensitive Help is no longer provided for </P>
<P>Microsoft Jet SQL, although online Help for Microsoft Jet SQL is still </P>
<P>included through the Help menu. Be sure to check the appropriate reference </P>
# P2 L1 H) S/ r<P>documentation for the SQL dialect of your database server when using either </P>
  C8 E  [% E& I<P>ODBCDirect connections or pass-through queries in Microsoft Jet-connected </P>
<P>client/server applications. </P>
<P>  </P>
<P>Use the dbSeeChanges constant in a Microsoft Jet workspace if you want to </P>
<P>trap changes while two or more users are editing or deleting the same record. </P>
<P>For example, if two users start editing the same record, the first user to </P>
; p8 f; p. r5 Z" v8 {3 B<P>execute the Update method succeeds. When the second user invokes the Update </P>
( j0 L% A4 k) I! {  u+ Q<P>method, a run-time error occurs. Similarly, if the second user tries to use </P>
<P>the Delete method to delete the record, and the first user has already </P>
. d% A) w6 E' I$ ?; D3 p$ O9 {# V" j<P>changed it, a run-time error occurs. </P>
3 A' b$ E* e! X: T- N<P>  </P>
<P>Typically, if the user gets this error while updating a record, your code </P>
<P>should refresh the contents of the fields and retrieve the newly modified </P>
<P>values. If the error occurs while deleting a record, your code could display </P>
<P>the new record data to the user and a message indicating that the data has </P>
<P>recently changed. At this point, your code can request a confirmation that </P>
; D5 R: a$ I6 }  b5 C<P>the user still wants to delete the record. </P>
<P>  </P>
9 k! Q, |+ V6 |- l6 l7 U1 f<P>You should also use the dbSeeChanges constant if you open a Recordset in a </P>
- Y* Q$ @1 h5 K" z<P>Microsoft Jet-connected ODBC workspace against a Microsoft SQL Server 6.0 (or </P>
3 b2 `0 u; j+ `( J9 @. n<P>later) table that has an IDENTITY column, otherwise an error may result. </P>
2 c  N/ G; V! `  w<P>  </P>
<P>In an ODBCDirect workspace, you can execute asynchronous queries by setting </P>
; @3 N0 p7 L  I' m9 Y<P>the dbRunAsync constant in the options argument. This allows your application </P>
- k+ U4 ]; `& u$ [5 e<P>to continue processing other statements while the query runs in the </P>
<P>background. But, you cannot access the Recordset data until the query has </P>
<P>completed. To determine whether the query has finished executing, check the </P>
<P>StillExecuting property of the new Recordset. If the query takes longer to </P>
& n7 i/ W0 ]  I) _: U* L<P>complete than you anticipated, you can terminate execution of the query with </P>
2 O, \/ ^+ @6 e0 x' O4 Z0 P/ @+ d<P>the Cancel method. </P>
2 G4 U1 Z% r2 y/ |2 x  ?/ N<P>  </P>
<P>Opening more than one Recordset on an ODBC data source may fail because the </P>
& t; j) x  n3 t( d# h4 O<P>connection is busy with a prior </P>
<P>OpenRecordset call. One way around this is to use a server-side cursor and </P>
0 K- M  W) T$ {" F  z<P>ODBCDirect, if the server supports this. Another solution is to fully </P>
<P>populate the Recordset by using the MoveLast method as soon as the Recordset </P>
& E: j* Z* U  h( k& q1 m7 N* Z<P>is opened. </P>
<P>  </P>
<P>If you open a Connection object with DefaultCursorDriver set to </P>
1 t3 K: ?/ `4 ]<P>dbUseClientBatchCursor, you can open a Recordset to cache changes to the data </P>
* z3 N, F5 T) n/ {/ R$ z7 z3 x) v$ _<P>(known as batch updating) in an ODBCDirect workspace. Include dbOptimisticBatc </P>
<P>h in the lockedits argument to enable update caching. See the Update method </P>
* H  o' z6 `% Y/ @% @/ t9 e<P>topic for details about how to write changes to disk immediately, or to cache </P>
& N3 n1 ~# S8 ]0 R, l<P>changes and write them to disk as a batch. </P>
; k: a6 B! ]1 O2 i8 n) b<P>  </P>
3 h1 g1 q* O8 f' `: s0 I: ^, V! b<P>Closing a Recordset with the Close method automatically deletes it from the </P>
8 t3 @0 E- h3 {* ]
<P>Recordsets collection. </P>
<P>  </P>
<P>Note   If source refers to an SQL statement composed of a string concatenated </P>
$ m5 ^/ g7 D' a8 F2 a! A; ^4 |<P>with a non-integer value, and the system parameters specify a non-U.S. </P>
<P>decimal character such as a comma (for example, strSQL = "PRICE &gt; " &amp; </P>
8 Q( Y0 }+ P5 Z2 r6 U/ O<P>lngPrice, and lngPrice = 125,50), an error occurs when you try to open the </P>
<P>Recordset. This is because during concatenation, the number will be converted </P>
+ T- l# S8 d9 F) M0 _! k$ [2 a! ]<P>to a string using your system's default decimal character, and SQL only </P>
<P>accepts U.S. decimal characters.</P>