怎样用ADO打开一个带密码的Access库？

韩冰

<>  </P>
( \, X5 n1 z4 X9 J# s7 q9 R<>Creates a new Recordset object and appends it to the Recordsets collection. </P>
<>  </P>
$ A/ \2 {. I; p% a5 i1 I& R, V<>Syntax </P>
" y' W* F) z8 B4 |& T<>  </P>
<>For Connection and Database objects: </P>
. B8 b- @, z  c3 y( e<>  </P>
1 l1 D0 U9 ]; Y0 q4 _  T8 E" `3 b  t<>Set recordset = object.OpenRecordset (source, type, options, lockedits) </P>
<>  </P>
<>For QueryDef, Recordset, and TableDef objects: </P>
<>  </P>
<>Set recordset = object.OpenRecordset (type, options, lockedits) </P>
: I9 a8 T( \6 M$ n- z<>  </P>
<>The OpenRecordset method syntax has these parts. </P>
<>  </P>
<>art    Description </P>
<>recordset       An object variable that represents the Recordset object you wantt to </P>
<>open. </P>
  F& r, a/ H: w8 L" c# _<>object  An object variable that represents an existing object from which you </P>
<>want to create the new Recordset. </P>
<>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>
' O4 k& |+ A, |: x<>returns records. For table-type Recordset objects in Microsoft Jet databases, </P>
8 p1 o  d% c5 f% z4 W0 k' b<>the source can only be a table name. </P>
' W% @) m) t" c0 P3 _& X3 \<>type    Optional. A constant that indicates the type of Recordset to open, as </P>
& N* T1 A3 q: c8 [+ I. u5 m0 C<>specified in Settings. </P>
0 x8 E! o$ }  C7 O<>options Optional. A combination of constants that specify characteristics of </P>
$ }! I' v; u5 k; p6 f% p1 M7 u<>the new Recordset, as listed in Settings. </P>
' D8 N4 Z$ {6 `2 s- |2 p<>lockedits       Optional. A constant that determines the locking for the Recordsset, </P>
! |3 _) @! M1 J% i5 L<P>as specified in Settings. </P>
<P>Settings </P>
5 C  b  `3 X# d5 Z# c<P>  </P>
) _  k- f7 ]+ f$ W2 Q, k' A<P>You can use one of the following constants for the type argument. </P>
<P>  </P>
<P>Constant        Description </P>
; j6 o! }3 c/ a" `+ {! D% _<P>  </P>
! B0 }( t) L3 r0 W# L<P>  </P>
* \/ m# y. |4 }6 t/ S% V3 v<P>dbOpenTable     Opens a table-type Recordset object (Microsoft Jet workspaces </P>
, a6 p) b2 b3 g: }, a3 |<P>only). </P>
<P>dbOpenDynamic   Opens a dynamic-type Recordset object, which is similar to an </P>
$ L( `" f2 q4 `% l* [<P>ODBC dynamic cursor. (ODBCDirect workspaces only) </P>
<P>dbOpenDynaset   Opens a dynaset-type Recordset object, which is similar to an </P>
9 l2 N: o9 L4 z( q' G- C<P>ODBC keyset cursor. </P>
<P>dbOpenSnapshot  Opens a snapshot-type Recordset object, which is similar to an </P>
<P>ODBC static cursor. </P>
<P>dbOpenForwardOnly?Opens a forward-only-type Recordset object. </P>
2 v0 j9 x; H5 J/ {, t- j<P>Note   If you open a Recordset in a Microsoft Jet workspace and you don't </P>
; a  J9 ?3 \4 v; H9 Q<P>specify a type, OpenRecordset creates a table-type Recordset, if possible. If </P>
, J1 q. H" C* O0 q<P>you specify a linked table or query, OpenRecordset creates a dynaset-type </P>
# e& @3 |: k9 I( V7 c<P>Recordset. In an ODBCDirect workspace, the default setting is dbOpenForwardOnl </P>
8 O1 X; O  t7 d, c: ~<P>y. </P>
" C& C; i2 [  t<P>  </P>
0 x# C( R- I5 L" }2 i, y<P>You can use a combination of the following constants for the options </P>
/ J4 ?6 p( b, x  z<P>argument. </P>
<P>  </P>
<P>Constant        Description </P>
<P>dbAppendOnly?Allows users to append new records to the Recordset, but </P>
9 D% \4 u( R/ c" p& K3 c<P>prevents them from editing or deleting existing records (Microsoft Jet </P>
* X" ?7 n2 R, k3 J0 s! X<P>dynaset-type Recordset only). </P>
<P>dbSQLPassThrough?Passes an SQL statement to a Microsoft Jet-connected ODBC </P>
<P>data source for processing (Microsoft Jet snapshot-type Recordset only). </P>
# |3 F% F3 ~! V4 B- I/ e# v& E<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>
1 ^8 ?5 `1 z) h, w5 T<P>useful in applications where multiple users have simultaneous read/write </P>
) k' J7 G3 A  |0 ^0 R<P>access to the same data. </P>
<P>dbDenyWrite?Prevents other users from modifying or adding records (Microsoft </P>
$ n$ H( G6 ~% V$ f, V<P>Jet Recordset objects only). </P>
<P>dbDenyRead?Prevents other users from reading data in a table (Microsoft Jet </P>
1 U1 j% L! S2 S6 q& J; x<P>table-type Recordset only). </P>
9 s/ `- M3 b' U: T/ M) b<P>dbForwardOnly?Creates a forward-only Recordset (Microsoft Jet snapshot-type </P>
<P>Recordset only). It is provided only for backward compatibility, and you </P>
<P>should use the dbOpenForwardOnly constant in the type argument instead of </P>
( X' N& [5 n' k5 J  w$ N<P>using this option. </P>
<P>dbReadOnly?Prevents users from making changes to the Recordset (Microsoft Jet </P>
<P>only). The dbReadOnly constant in the lockedits argument replaces this </P>
<P>option, which is provided only for backward compatibility. </P>
! k; C* Y- o5 b# v/ e+ b<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>
# M- t# Q1 ]! M6 w- E( o<P>dbConsistent?Allows only consistent updates (Microsoft Jet dynaset-type and </P>
2 W# y( C" m. k, I<P>snapshot-type Recordset objects only). </P>
<P>Note   The constants dbConsistent and dbInconsistent are mutually exclusive, </P>
; N' ~  J' N9 a* J  v<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>
<P>You can use the following constants for the lockedits argument. </P>
/ x' P% [. h9 [/ e% W<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>
. E7 ~& |9 A, P- ^. _2 K( ^<P>run-time error occurs. </P>
/ O2 _' \: z+ t% U4 B( {<P>dbPessimistic?Uses pessimistic locking to determine how changes are made to </P>
4 v1 W5 O# ^( H8 |# z# |2 L9 o<P>the Recordset in a multiuser environment. The page containing the record </P>
! M( U" F* F: t' k<P>you're editing is locked as soon as you use the Edit method (default for </P>
- t0 V2 ^# e' ]6 }6 R9 T<P>Microsoft Jet workspaces). </P>
<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>
$ Y- o% y3 |7 W$ T9 C/ x' b( [<P>locked until the Update method is executed. </P>
# f* \& \+ z  U1 s5 g6 [+ U( ?<P>dbOptimisticValue?Uses optimistic concurrency based on row values (ODBCDirect </P>
1 [  _0 e, T4 F4 v4 F; _5 |<P>workspaces only). </P>
9 G# y0 w# Z2 u; m( e! ~+ [. h<P>dbOptimisticBatch?Enables batch optimistic updating (ODBCDirect workspaces </P>
/ l6 ~0 f; z2 v<P>only). </P>
<P>Remarks </P>
7 g+ t9 y/ k, C<P>  </P>
8 i. S2 }3 `7 R2 f<P>In a Microsoft Jet workspace, if object refers to a QueryDef object, or a </P>
4 r( v. m; A  k' x) E" m<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>
9 M  n. V& r- B% [! A$ w<P>the type argument; if you do, a run-time error occurs. If you want to use an </P>
, b& B( S/ M) ^+ u- l- x7 U<P>SQL pass-through query on a linked table in a Microsoft Jet-connected ODBC </P>
<P>data source, you must first set the Connect property of the linked table's </P>
: M+ m. w/ m# t7 y* G<P>database to a valid ODBC connection string. If you only need to make a single </P>
, j  B0 d" T- D% z" O5 P+ a9 A<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>
<P>argument. </P>
<P>  </P>
<P>If object refers to a dynaset- or snapshot-type Recordset, the new Recordset </P>
3 O! V( R) V8 B, x) d) D2 S<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, G, S3 }" O6 g; _* I$ e) ?- r. |<P>dynaset-type Recordset. You can't open new Recordset objects from forward-only </P>
9 c* y6 `2 W6 D. r5 V" C# }3 J<P>杢ype or ODBCDirect Recordset objects. </P>
<P>In an ODBCDirect workspace, you can open a Recordset containing more than one </P>
$ O! J+ O' [0 z  H* A- q$ l0 V; P<P>select query in the source argument, such as </P>
<P>  </P>
# |( s$ f1 R# H; M+ F<P>"SELECT LastName, FirstName FROM Authors </P>
<P>WHERE LastName = 'Smith'; </P>
$ \( w4 ], m4 f) P9 L9 g  L+ m<P>SELECT Title, ISBN FROM Titles </P>
<P>WHERE ISBN Like '1-55615-*'" </P>
( u+ ]" s: r9 z: ~<P>  </P>
$ {" i* E! {' ~6 D: }3 a<P>The returned Recordset will open with the results of the first query. To </P>
<P>obtain the result sets of records from subsequent queries, use the </P>
<P>NextRecordset method. </P>
& b% K* o) W8 \5 H+ ~. ?<P>  </P>
* t, O* V6 V/ O3 w9 [<P>Note   You can send DAO queries to a variety of different database servers </P>
2 G2 s( @9 m* d3 v<P>with ODBCDirect, and different servers will recognize slightly different </P>
5 E- a7 T6 H7 y9 B<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>
5 Z2 g  v9 U4 L$ c6 j4 f<P>documentation for the SQL dialect of your database server when using either </P>
2 m$ |* F8 w1 [' w) Z0 Y$ J$ B5 g! L<P>ODBCDirect connections or pass-through queries in Microsoft Jet-connected </P>
<P>client/server applications. </P>
5 i. R* b& S8 z8 J# Y<P>  </P>
) [- x) ?7 B8 {4 [7 [<P>Use the dbSeeChanges constant in a Microsoft Jet workspace if you want to </P>
* y; ~9 B/ a% r- t# i<P>trap changes while two or more users are editing or deleting the same record. </P>
# {' l$ ^3 Q# b3 \- q<P>For example, if two users start editing the same record, the first user to </P>
7 [& Y) q" _, p* f' F( Q<P>execute the Update method succeeds. When the second user invokes the Update </P>
. Y! j9 r. k0 r) G<P>method, a run-time error occurs. Similarly, if the second user tries to use </P>
9 }6 j; `) I; k; @( E& x7 f<P>the Delete method to delete the record, and the first user has already </P>
) I2 |* }3 g1 A) Q. g; Y- g<P>changed it, a run-time error occurs. </P>
/ K. B* k. X5 T# G% j/ I<P>  </P>
<P>Typically, if the user gets this error while updating a record, your code </P>
) J9 P+ ?4 o) N( a<P>should refresh the contents of the fields and retrieve the newly modified </P>
8 z/ M( \# @' v2 N9 \<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>
. H' `0 [% {. O  t# t7 q<P>the user still wants to delete the record. </P>
2 `- x$ T6 m& A; d) j6 ?* x<P>  </P>
/ M) {" X7 V" A, l5 ]0 E* A9 y* U<P>You should also use the dbSeeChanges constant if you open a Recordset in a </P>
' c, W  |- b& Y3 f, w3 b. Y<P>Microsoft Jet-connected ODBC workspace against a Microsoft SQL Server 6.0 (or </P>
' n5 h: w8 e- S  f- n# E9 w, N<P>later) table that has an IDENTITY column, otherwise an error may result. </P>
1 n& [/ y1 _5 x8 z# j/ n- ~5 F<P>  </P>
3 ?' T; @3 D4 P" V0 E1 S<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>
0 g% O8 O2 Q- s" e4 g<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>
8 v8 U! d% w9 e% `0 }<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>
<P>complete than you anticipated, you can terminate execution of the query with </P>
' i3 N& [9 o7 g<P>the Cancel method. </P>
<P>  </P>
; e" J! G4 d7 V$ |9 {* ^! j<P>Opening more than one Recordset on an ODBC data source may fail because the </P>
4 l3 u* m" N9 P) S<P>connection is busy with a prior </P>
<P>OpenRecordset call. One way around this is to use a server-side cursor and </P>
6 Q- F2 E- W: ~<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>
2 n* m# t/ U! [" Z<P>is opened. </P>
2 @4 ?* @. B1 r/ X# S<P>  </P>
9 l& A" ?1 ^$ P3 \  t2 @<P>If you open a Connection object with DefaultCursorDriver set to </P>
<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>
  q0 A/ i, }; ^& V  ?<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>
$ t% ?" k4 |9 s) M<P>Closing a Recordset with the Close method automatically deletes it from the </P>
8 ^3 p6 A; K: E0 p+ F
3 m( m: k4 G) N  B  K: N0 G<P>Recordsets collection. </P>
<P>  </P>
<P>Note   If source refers to an SQL statement composed of a string concatenated </P>
) V9 u, ?8 c$ T& ^5 N6 r0 Y<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>
2 |% f; t0 i) f9 B! y9 ]4 Q<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>
- _3 a/ Q6 D0 `$ B# M<P>to a string using your system's default decimal character, and SQL only </P>
<P>accepts U.S. decimal characters.</P>