怎样用ADO打开一个带密码的Access库？

韩冰

<>  </P>
<>Creates a new Recordset object and appends it to the Recordsets collection. </P>
( ~  O. D1 j' x( P* `8 S% C# F<>  </P>
<>Syntax </P>
<>  </P>
<>For Connection and Database objects: </P>
+ Z. }% f. n& n! E1 e: f, q<>  </P>
<>Set recordset = object.OpenRecordset (source, type, options, lockedits) </P>
<>  </P>
<>For QueryDef, Recordset, and TableDef objects: </P>
<>  </P>
+ k7 c1 p- Y9 I& M6 S* P<>Set recordset = object.OpenRecordset (type, options, lockedits) </P>
<>  </P>
<>The OpenRecordset method syntax has these parts. </P>
<>  </P>
<>art    Description </P>
$ ^0 W4 ~9 L9 I9 O" _  p<>recordset       An object variable that represents the Recordset object you wantt to </P>
<>open. </P>
, U) {8 w% \  x8 `4 l$ t' }<>object  An object variable that represents an existing object from which you </P>
+ x, E  V9 {. y<>want to create the new Recordset. </P>
0 o! M. R3 b+ o7 ]4 E! }<>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>
1 W; _" ^) A# I1 a: p/ Q/ v5 t" _3 B8 a<>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>
8 R0 W/ d  G3 ?<>options Optional. A combination of constants that specify characteristics of </P>
, R4 x- t9 U! Q0 _! C<>the new Recordset, as listed in Settings. </P>
+ l0 R& q& w, p& v+ `/ U' x, Y<>lockedits       Optional. A constant that determines the locking for the Recordsset, </P>
<P>as specified in Settings. </P>
' f1 h/ G8 m& X( |<P>Settings </P>
<P>  </P>
<P>You can use one of the following constants for the type argument. </P>
0 m# j; l1 u/ `' i( \<P>  </P>
3 m' C: X% R* q4 P, _9 c<P>Constant        Description </P>
<P>  </P>
<P>  </P>
; a: Y, R: p) q3 d<P>dbOpenTable     Opens a table-type Recordset object (Microsoft Jet workspaces </P>
<P>only). </P>
9 S7 A8 w( g, K, i2 l<P>dbOpenDynamic   Opens a dynamic-type Recordset object, which is similar to an </P>
<P>ODBC dynamic cursor. (ODBCDirect workspaces only) </P>
  e) z. [' r- B( g4 B2 F<P>dbOpenDynaset   Opens a dynaset-type Recordset object, which is similar to an </P>
0 }7 w7 ]: k5 I' X! M<P>ODBC keyset cursor. </P>
- j$ h4 y" G& M, C( |<P>dbOpenSnapshot  Opens a snapshot-type Recordset object, which is similar to an </P>
<P>ODBC static cursor. </P>
; M( G+ a) }. n( ]0 T5 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>
  ^  Q& P7 [% ?# u* a* S<P>you specify a linked table or query, OpenRecordset creates a dynaset-type </P>
. f7 y: p) Q. k) O2 U5 _<P>Recordset. In an ODBCDirect workspace, the default setting is dbOpenForwardOnl </P>
; w  O; U& a: a/ ^8 d2 A  }7 R. E<P>y. </P>
<P>  </P>
1 T0 g. S) o7 V+ D! f1 w3 I<P>You can use a combination of the following constants for the options </P>
<P>argument. </P>
6 V+ Y2 J/ X3 O7 K$ I4 v<P>  </P>
<P>Constant        Description </P>
<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>
<P>dynaset-type Recordset only). </P>
$ C6 N7 e% ]$ U$ K) }% L4 v* `<P>dbSQLPassThrough?Passes an SQL statement to a Microsoft Jet-connected ODBC </P>
; w. m( U( ^+ p4 F- i<P>data source for processing (Microsoft Jet snapshot-type Recordset only). </P>
<P>dbSeeChanges    Generates a run-time error if one user is changing data that </P>
<P>another user is editing (Microsoft Jet dynaset-type Recordset only). This is </P>
<P>useful in applications where multiple users have simultaneous read/write </P>
  C8 B2 Y2 U& P+ W8 L<P>access to the same data. </P>
/ o3 V# q( }; S% I) I/ l3 X! _<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>
4 C& }4 C/ q2 ^% X3 T<P>table-type Recordset only). </P>
<P>dbForwardOnly?Creates a forward-only Recordset (Microsoft Jet snapshot-type </P>
, l/ Q- h8 B0 h3 Q3 A+ j<P>Recordset only). It is provided only for backward compatibility, and you </P>
2 V# B3 E: F. o, t  B3 T<P>should use the dbOpenForwardOnly constant in the type argument instead of </P>
$ o7 n% ^) y8 a1 {4 E<P>using this option. </P>
3 [2 f7 S7 Q3 w! |+ u<P>dbReadOnly?Prevents users from making changes to the Recordset (Microsoft Jet </P>
- F5 V/ P& d, O4 f; ~. p7 p3 x<P>only). The dbReadOnly constant in the lockedits argument replaces this </P>
<P>option, which is provided only for backward compatibility. </P>
# P; X; [3 d1 K1 M; k5 ~' J<P>dbRunAsync      Runs an asynchronous query (ODBCDirect workspaces only). </P>
<P>dbExecDirect?Runs a query by skipping SQLPrepare and directly calling </P>
<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>
<P>the "Microsoft ODBC 3.0 Programmer抯 Reference." </P>
<P>dbInconsistent?Allows inconsistent updates (Microsoft Jet dynaset-type and </P>
<P>snapshot-type Recordset objects only). </P>
" q- K, a9 k3 h/ G<P>dbConsistent?Allows only consistent updates (Microsoft Jet dynaset-type and </P>
<P>snapshot-type Recordset objects only). </P>
<P>Note   The constants dbConsistent and dbInconsistent are mutually exclusive, </P>
' }# L) \: e2 [! z; I- R<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>
4 r% E% K+ g3 m' k& u0 d4 M<P>You can use the following constants for the lockedits argument. </P>
9 u) V9 S# t1 L4 j9 l<P>  </P>
<P>Constant        Description </P>
<P>dbReadOnly      Prevents users from making changes to the Recordset (default for </P>
0 h$ ]  B' \3 i2 p7 f. @; O( ]<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>
<P>run-time error occurs. </P>
3 J" q" L7 T% |<P>dbPessimistic?Uses pessimistic locking to determine how changes are made to </P>
  |  t6 v7 K' E+ }<P>the Recordset in a multiuser environment. The page containing the record </P>
<P>you're editing is locked as soon as you use the Edit method (default for </P>
<P>Microsoft Jet workspaces). </P>
, V# E, a* m9 t3 q4 L( `) c<P>dbOptimistic?Uses optimistic locking to determine how changes are made to the </P>
<P>Recordset in a multiuser environment. The page containing the record is not </P>
8 s% ?. e; i9 D  y% P- w<P>locked until the Update method is executed. </P>
<P>dbOptimisticValue?Uses optimistic concurrency based on row values (ODBCDirect </P>
- e3 r6 k2 Z; C" [% N8 {# s<P>workspaces only). </P>
+ b9 e2 r$ n6 f- R4 a/ u% O<P>dbOptimisticBatch?Enables batch optimistic updating (ODBCDirect workspaces </P>
<P>only). </P>
<P>Remarks </P>
<P>  </P>
% w& B3 }9 n0 L+ X9 {<P>In a Microsoft Jet workspace, if object refers to a QueryDef object, or a </P>
# W7 V* n" \0 |. [<P>dynaset- or snapshot-type Recordset, or if source refers to an SQL statement </P>
<P>or a TableDef that represents a linked table, you can't use dbOpenTable for </P>
; k# D0 Y' |! j( f, u<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>
2 k# ]) b! i# U! j3 C+ r<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>
<P>source, you can improve performance by using dbOpenForwardOnly for the type </P>
* l' p- i! Q6 @<P>argument. </P>
<P>  </P>
$ T6 L* y- `1 N. w<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>
+ J" Z6 E' Q  _+ W9 x2 l. j<P> refers to a table-type Recordset object, the type of the new object is a </P>
<P>dynaset-type Recordset. You can't open new Recordset objects from forward-only </P>
<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>
5 c4 j2 f" r$ e, t' s+ ^<P>  </P>
<P>"SELECT LastName, FirstName FROM Authors </P>
) a6 G7 F8 w; l2 g1 E8 f! ~<P>WHERE LastName = 'Smith'; </P>
<P>SELECT Title, ISBN FROM Titles </P>
4 H, R3 E& o- q. ^$ |# B! V1 D<P>WHERE ISBN Like '1-55615-*'" </P>
<P>  </P>
% m9 }9 Y" U, A: G) e8 F<P>The returned Recordset will open with the results of the first query. To </P>
2 p7 n5 d0 l* g<P>obtain the result sets of records from subsequent queries, use the </P>
3 g& ]+ m, o8 q. n2 n0 {<P>NextRecordset method. </P>
<P>  </P>
<P>Note   You can send DAO queries to a variety of different database servers </P>
9 W6 S/ O3 S) i, }7 D<P>with ODBCDirect, and different servers will recognize slightly different </P>
  E$ R7 Z# R- P( V/ Q8 Q$ w<P>dialects of SQL. Therefore, context-sensitive Help is no longer provided for </P>
! K2 l: U3 Y7 m! l# R! r<P>Microsoft Jet SQL, although online Help for Microsoft Jet SQL is still </P>
, m( I- `; L6 _; F- `( U  p7 S<P>included through the Help menu. Be sure to check the appropriate reference </P>
<P>documentation for the SQL dialect of your database server when using either </P>
<P>ODBCDirect connections or pass-through queries in Microsoft Jet-connected </P>
<P>client/server applications. </P>
; k8 H( N8 b/ k8 H: z<P>  </P>
/ ?( a' N: C6 l' x<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>
' U5 X% N( J/ q" m! B0 v<P>For example, if two users start editing the same record, the first user to </P>
/ U( Q- D& F6 e. A# V3 l" S1 G# c1 n3 G<P>execute the Update method succeeds. When the second user invokes the Update </P>
. _# z0 l0 m" F/ [2 }<P>method, a run-time error occurs. Similarly, if the second user tries to use </P>
5 J) H% C6 h, S<P>the Delete method to delete the record, and the first user has already </P>
<P>changed it, a run-time error occurs. </P>
<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>
- d/ f. H3 |7 A<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>
<P>the user still wants to delete the record. </P>
<P>  </P>
' T7 J' ]! a1 Y+ ]: u<P>You should also use the dbSeeChanges constant if you open a Recordset in a </P>
<P>Microsoft Jet-connected ODBC workspace against a Microsoft SQL Server 6.0 (or </P>
9 Y$ R' d  j; N# A/ j  t<P>later) table that has an IDENTITY column, otherwise an error may result. </P>
! G; K- n+ q3 x' g<P>  </P>
<P>In an ODBCDirect workspace, you can execute asynchronous queries by setting </P>
<P>the dbRunAsync constant in the options argument. This allows your application </P>
3 m) E& ?" k( ?' u$ Z<P>to continue processing other statements while the query runs in the </P>
8 O; F" a& ?/ G* r7 a! w<P>background. But, you cannot access the Recordset data until the query has </P>
8 L. N5 j) x$ P3 J. W5 H<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>
' i( h4 H  u) }% @<P>complete than you anticipated, you can terminate execution of the query with </P>
0 @2 C4 x) n* f4 p- l. G" V! C% P9 [<P>the Cancel method. </P>
<P>  </P>
$ ^2 e- q' G- ?5 F6 ?+ j$ r; w<P>Opening more than one Recordset on an ODBC data source may fail because the </P>
# @# P; T2 A1 j9 R8 J5 s3 ~<P>connection is busy with a prior </P>
<P>OpenRecordset call. One way around this is to use a server-side cursor and </P>
<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>
: F" ^6 E7 X; N) S9 u! i  x<P>is opened. </P>
<P>  </P>
5 M' o) |% V. B( A! q2 E, v& G<P>If you open a Connection object with DefaultCursorDriver set to </P>
( ?: _$ x4 d4 f: ^<P>dbUseClientBatchCursor, you can open a Recordset to cache changes to the data </P>
<P>(known as batch updating) in an ODBCDirect workspace. Include dbOptimisticBatc </P>
9 l+ [! {! v7 V2 l1 S3 |' N<P>h in the lockedits argument to enable update caching. See the Update method </P>
<P>topic for details about how to write changes to disk immediately, or to cache </P>
<P>changes and write them to disk as a batch. </P>
<P>  </P>
2 e+ `3 r4 W$ N- @$ ]<P>Closing a Recordset with the Close method automatically deletes it from the </P>
( a3 n8 ]* R8 i' P5 y
<P>Recordsets collection. </P>
0 s- K+ }# I( o* T3 w<P>  </P>
/ r9 D1 e# A2 e$ ?% L( W<P>Note   If source refers to an SQL statement composed of a string concatenated </P>
<P>with a non-integer value, and the system parameters specify a non-U.S. </P>
5 ]5 {8 f6 {8 @9 @( |<P>decimal character such as a comma (for example, strSQL = "PRICE &gt; " &amp; </P>
<P>lngPrice, and lngPrice = 125,50), an error occurs when you try to open the </P>
2 R; ?3 y3 k7 y" G3 ?5 g! Q, }- a<P>Recordset. This is because during concatenation, the number will be converted </P>
6 a4 O2 ^! M, |+ s9 D<P>to a string using your system's default decimal character, and SQL only </P>
<P>accepts U.S. decimal characters.</P>