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update statement sent to the database. Normally, you only need to specify the primary key in the WHERE clause to uniquely identify the row to be updated. However, in a multiuser environment, you might want to include more columns to ensure that no other user has altered the record between the time you retrieved the row and the time you update it. For instance, if you specify your WHERE clause, include all columns from the record; then if the WHERE clause fails, you know that the record has been altered. Use dbCriteriaKey if you only want to use the primary columns in the WHERE clause. dbCriteriaModValues causes the WHERE clause to include the primary columns and any columns that were changed. Use this option if you are concerned about concurrency issues (see Chapter 11 for more details) but only care about those columns that you altered. dbCriteraAllCols uses all columns in the WHERE clause. Use this option in a multiuser environment where you absolutely do not want to alter a record if another user has altered it. dbCriteriaTimeStamp will use the primary columns and the timestamp column if there is one. This is often just as good as dbCriteriaAllCols because any change to the record will cause the timestamp to be changed, and it is more efficient (because the WHERE clause is simpler). Along with any of the five prior constants, you can also specify either dbCriteriaUpdate to specify that the update be done with an UPDATE statement or dbCriteriaDeleteInsert to specify that the update be done by first deleting the record and then inserting a new one. Normally, you will want to use dbCriteriaUpdate (which is the default) because it is inherently more efficient. However, if for some reason you are altering the primary key, you normally need to delete the first record and then insert a new record. • The ValidationRule and ValidationText properties (Jet workspace only) control the validation criteria and what message to display if the record fails validation. I generally recommend validating each field in the RecordSet independently. Note, however, that the ValidationRule for a Field object cannot reference other Field objects, whereas the ValidationRule for a RecordSet can reference any field in the record. I discussed these properties earlier in the chapter in the TableDef and Field topics. Products | Contact Us | About Us | Privacy | Ad Info | Home Previous Table of Contents Next Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc. All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement.
Brief Full Advanced Search Search Tips To access the contents, click the chapter and section titles. Visual Basic 6 Client/Server Programming Gold Book (Publisher: The Coriolis Group) Author(s): Michael MacDonald and Kurt Cagle ISBN: 1576102823 Publication Date: 10/01/98 Search this book: Previous Table of Contents Next The RecordSet object has a rich set of methods that you use to manipulate fields or data as well as properties. Not all methods are available for all record set types, as noted in the discussion of each: • The AddNew method adds a new record to the RecordSet. It does not add it to the database. (Use the Update method to make the change to the database.) If the fields have default values, they are set to those values; otherwise, they are set to Null. If you create a new record and then move to another record, the changes are lost unless you first invoke the Update method (unless you are performing batch updates). In a dynaset-type RecordSet, new records are always added to the end of the RecordSet. In a table-type RecordSet, records are added in their proper sort order if one has been specified with the Index property. The new record must have a unique key. If there is no unique key, Jet workspaces generate a “Permission Denied” error, whereas ODBCDirect workspaces generate the message “Invalid Argument.” • The Cancel method (ODBCDirect workspace only) cancels execution of a currently running asynchronous query (for the RecordSet object, this is the OpenRecordSet method) or MoveLast operation. If dbRunAsync was not specified, using Cancel causes a runtime error. • CancelUpdate cancels any changes that are pending since the last Update call. If the user adds a record or modifies a record, the changes are discarded. If performing batch updating, you can also specify an argument, as shown in the following example. dbUpdateRegular cancels any pending changes that aren’t cached. This is the default. dbUpdateBatch cancels any changes pending in the cache. rsEmp.CancelUpdate dbUpdateBatch • Clone (Jet workspace only) creates a copy of the current record set. The bookmarks in each copy of the RecordSet are shared, but each RecordSet can have different current records. You can issue the Clone method on the cloned RecordSet without affecting the original RecordSet and you can issue another Clone on the original RecordSet without affecting the cloned RecordSet. Cloning a RecordSet is useful if you need to access the records in different ways at the same time, and it is more efficient than creating a second RecordSet using the CreateRecordSet method. The following example creates a cloned RecordSet and searches it to see if the primary key
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Brief Full Advanced Search Search T
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The Active Data Control Where To Go
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Index Products | Contact Us | About
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technology. We have kept our eye to
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people checked each piece of code.
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and sell through your Web site. (Tr
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grammatical correctness. Kris offer
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In this chapter, I introduce the un
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example, a “high-speed” Etherne
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which customers are from the state
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COM automatically “knows” how t
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little more than present forms, men
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Figure 1.4 The beginning of a simpl
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IBM’s Token Ring architecture run
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application to application. The IP
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Any database that organizes data in
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proper choice is highly dependent o
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equire the database to work too har
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You might want to consider the fina
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integrated well with XDB. The choic
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The columns correspond to fields in
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In this example, the database autom
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places, such as 1.25. An irrational
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key, we assign one to the Student_C
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Second normal form, usually abbrevi
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might want to consider selectively
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This example adds a column named Em
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(such as being only ‘M’ or ‘F
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Previous Table of Contents Next Pro
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query result. (I expanded upon this
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If your database does not provide a
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You can join together more than two
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SELECT EMP_NO AS 'NUMBER', EMP_LNAM
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FROM EMPLOYEE The result is: MIN(EM
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GENEVIEVE WESLEY The LTRIM function
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(15, 2) returns 1 because 15 divide
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SELECT SUM(EMP_SALARY) FROM EMPLOYE
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300 66958.36 400 53983.02 You can n
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ORDER BY EMP_DEPT_NO The output of
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SELECT EMP_NO, EMP_FNAME, EMP_LNAME
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the ODBC API as a means of database
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DAO/Jet * 4 7 5 6 DAO/ODBCDirect Da
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Listing 4.1 opens three files (in A
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Dim sBuffer As String * 512 Get #iF
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ODBCDirect was added to DAO with ve
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later in this chapter. For new rela
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End Sub Figure 4.5 The Employee app
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Listing 4.3 Code from frmDSNList. P
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When placing a data-aware control o
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Str$(Adodc1.RecordSet.RecordCount)
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similar to general modules in that
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source to other objects, including
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If bCancel Then adStatus = adStatus
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Structured Query Language, which li
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Figure 5.1 DAO objects in the Jet w
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dbVersion11 new_db will be the Jet
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collection after database operation
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dbDecimal Decimal dbDouble Double d
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Page 181 and 182: nested transactions in an ODBCDirec
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Page 187 and 188: three properties: Name, Password, a
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Page 193 and 194: QueryDef object and thus omits the
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Page 231: each record in the RecordSet. The c
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Page 239 and 240: chapter provides an example of usin
Page 243 and 244: End Sub Table 5.15 Constants for th
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Page 247 and 248: doEngine object is created. Additio
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Page 253 and 254: in an rdoEnvironment object, all rd
Page 257 and 258: If cSalary !emp_Salary Then ' If c
Page 259 and 260: password parameters are not supplie
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Page 263 and 264: Command1(0).Enabled = True Command1
Page 265 and 266: Dim vErr As rdoError For Each vErr
Page 267 and 268: objects. If the query was successfu
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Page 275 and 276: embrace where two processes lock ea
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If MsgBox(sMsg, vbYesNo & vbQuestio
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pbStatus.Value = .PercentPosition D
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cannot be updated. If the columns r
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Dim vArray As Variant ' Get 100 row
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modified. You can set the Cancel ar
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The SourceColumn and SourceTable pr
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stored procedures from Visual Basic
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Figure 6.6 The RDO parameters demon
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Private Sub MSRDC1_Error(Number As
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Products | Contact Us | About Us |
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With VB6 comes MDAC 2.0, which adde
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Remote Data Services (RDS) is a dev
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adGUID Globally unique identifier (
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(ByVal pError As ADODB.Error, _ adS
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that few records are affected and a
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adXactChaos (Default.) Cannot overw
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(adSchemaTables, Array(Empty, Empty
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Dim sTable As String sTable = lbTab
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Figure 7.6 Message from the data so
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A value of 0 specifies that there i
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• The Direction property is used
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To move through a set of records, y
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ByVal pRecordset As ADODB.Recordset
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adOpenStatic. If you will be perfor
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as an argument the number of record
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FileName argument is self-explanato
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OriginalValue property contains the
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ADO, RDO, and DAO are roughly analo
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it exploits enough different method
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"UID=Coriolis;PWD=Coriolis" Set aco
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You must modify the connection stri
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' Display the results With arsRepor
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Objects library to Microsoft Active
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lbTables(0).AddItem ars.Fields(1).V
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e automatically created (!). To use
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eing the data source of a Command o
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default caption. I did this for the
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4. Now, you will need to add naviga
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txtRaise(2) = deStoredProcedure.Com
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object’s name by prefixing it wit
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The DataReport object supports a nu
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Command object represents a band in
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ight-click on the Flexgrid control
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Select Case dir Case rsFirst rs.Mov
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ByVal pConnection As ADODB.Connecti
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If IsNull(rs(iRs).Fields(iCtr - iSt
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possible. In fact, the nature of VB
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To map the properties, select Proce
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object in component based developme
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If Len(first) = 0 Or Len(last) = 0
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Figure 10.2 Once you declare a refe
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Private Sub Graphics_PrintIt(Target
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The next example modifies the Print
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End Select End Sub I will show you
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sMsg = "The following errors were e
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Private WithEvents empCLSDemo As cl
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triggered. In that event, I invoke
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Why go to all this trouble? Figure
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object. In a sense, the class modul
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Optimizing Cross-Process Calls As n
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start it in a separate instance of
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this method remotely, and I was for
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.Height = (iIndex * 360) + 1850 .Sh
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All of the code in both the remote
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the data dictionary. I will then le
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number of solutions. Previous Table
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CTRY_NAME VARCHAR (35) NOT NULL, CO
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dd_desc VARCHAR (64), CONSTRAINT PK
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Public when the application opens:
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cannot take an Oracle stored proced
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efficient), I chose to use the sp_l
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' Command object for the stored pro
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End Function When ADO dynamically c
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RETURN ; END IF ; /* If country sta
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FROM data_dic WHERE dd_type = old_d
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Figure 11.3 The Data Dictionary Mai
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data type—its underlying data typ
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CommitTrans Else RollbackTrans End
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any money. At worst, it should at l
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update to Cindy failed but the upda
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UPDATE employee SET emp_salary = 50
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difficult to update. With XML, the
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Raining on and off throughout the
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library in your Visual Basic projec
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ReplaceNode Replaces one node with
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Public WithEvents DownloadTimer As
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Sunny and hot. Raining on a
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Of course, it would be useful to ge
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Recursion is a powerful programming
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Dim Index As Integer Dim tempNode A
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End Sub You could create a simple X
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Figure 12.4 A DTD makes it much eas
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The DTD is contained as part of th
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In addition to enumerated lists, th
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Skies will be clear and warm today,
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which relies heavily on line breaks
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&ALABAMA; &ALASKA; &ARIZONA; ... &W
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can also leverage the powers of DHT
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information, usually a structured s
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somewhat in sales. IIS introduced A
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client side scripting is fully visi
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happening than just the creation of
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Cookies A collection of cookies tha
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8. Select the WeatherSummary object
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for all these possible additional p
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• Query strings have a limit of 1
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eturns it as a formatted string. Fu
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The Daily Post As mentioned previou
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4. Double-click the weatherSubmitFo
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If Request.Form("Forecast")="" then
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shows the actual Web event connecti
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in the record are modified and then
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the list of all states, ordered by
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Response.Write "" Response.Write Re
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same format as a rainfall map. A We
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still using Internet Explorer 3.x a
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Figure 14.5 The standard Properties
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Figure 14.10). Notice that the docu
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The highlighted code in Listing 14.
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CtrlKey Boolean True if the Ctrl ke
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collections, many of which are cove
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ClearInterval(timerID as Long) Clea
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Prompt(msg as String, defaultStr as
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OuterText=textString OuterText=“T
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Mouse Data The STYLE=“positio
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as a or paragraph element, accumul
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Dim expn As String expn = TextData
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uffer = buffer + expn WriteLn = exp
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Dim rowOS as COStream 'Set the dest
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example, if you wish to retrieve th
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Dim cell As HTMLTableCell Dim row A
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While on the subject of the parentW
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Understanding Input Text boxes and
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High Temperature:° F Low Tempe
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For index = 0 To lbCtrl.Length - 1
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Exit For End If Next RS.Close conn.
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State = States.Value Set WeatherTab
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Scrollbars Built into containers Th
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A little searching reveals that, in
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Set opt = Document.createElement("O
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Figure 15.1 The Project Properties
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HSPACE=0 > 2. Create a new DHTML
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loop Img.loop=3 Indicates the numbe
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useMap Img.useMap=“#MyMap” Prov
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there are times (especially with We
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associating code as with ExecFuncti
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tools. The tag demonstrates both t
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style rules that you need, as shown
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posLeft, MyDiv.style.posLeft=20 Set
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This is some text This is anoth
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sheet’s rule. Listing 15.7 The Ge
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slt=document.parentWindow.confirm("
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Answer=window.showModalDialog(URL,a
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Visual Basic 6 includes two new use
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ibliography at the end of this chap
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The calendar object is de
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Comment.Value = Replace(RS("Comment
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goods at all stages of production,
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DEPT_LOC_ID CHAR (3) NOT NULL, DEPT
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ALTER TABLE LINE_ITEM ADD CONSTRAIN
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COMMIT, ROLLBACK, And LOCK ANSI SQL
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VAR returns the variance (the squar
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RDO is loaded instead. However, whe
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Level 2 Conformance Requirements
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objects, 374 proxy objects and, 18
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B Application Wizard, 125, 619 Appl
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C Bound controls, 202 Boyce-Code no
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doConnection object, 235 rdoResults
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Connection object, 278 parameters,
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Microsoft Jet and, 105 object cross
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QueryTimeOut property, 159 RecordsA
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Debug mode, 618 DECIMAL (38) data t
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E Documents collection, 138, 168-16
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F properties, 288 Source property,
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G FLOATING POINT data type, 46 Floa
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I Hello World application, 511-514,
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delegation, 122 reuse, 121-122 Inhe
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doResultset object, 245-246 RecordS
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N MIN function, 79, 80 Minimum ODBC
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O NodeValue property, 472 NoMatch p
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P OpenSchema method, 284, 324, 327-
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Q prop_type string, 148 prop_val st
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licensing fees, 35 Lotus Approach,
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doCreateEnvironment property (rdoEn
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doVersion property (rdoEngine objec
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ValidationText property, 196 Record
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S ResultChanged event (rdoResultset
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Snapshot-type record set, 189 SNF.
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T Strings, 45 XML attribute values
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U Connection object, 165 rdoConnect
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W RecordSet object, 196 TableDef ob
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X Type property, 151 UserName prope
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