Visual Basic 6 Client/Server Programming Gold Book:Table of ...

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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: Numeric Data Previous Table of Contents Next Unlike character data, numeric data can take many forms and vary more from RDBMS to RDBMS than other data types. In general, you will run into the following data types (refer to your vendor’s documentation for any specifics or differences in implementation): • NUMERIC (S, P)—S stands for scope and P stands for precision. Scope refers to how many digits the number is allowed to hold, and precision refers to how many of those numbers are to the right of the decimal place, as in the following example: Ord_Amount NUMERIC (11,2) In this example, the largest number that can be stored is 999,999,999.99. Even if your number has no digits to the right of the decimal place, you can use only nine to the left of the decimal point. Thus, a column defined as NUMERIC (4,4) can be no larger than 0.9999. • INTEGER is a data type that holds a whole number from –32,768 to +32,767. An UNSIGNED INTEGER is capable of holding positive whole numbers from 0 to 65,536. • LONG numbers can be any whole number of approximately negative 2.1 billion to positive 2.1 billion. As with the INTEGER data type, your database may also support an unsigned variation, UNSIGNED LONG, which holds a positive whole number of 0 to approximately 4.2 billion. • FLOATING POINT, SINGLE, SINGLE PRECISION, DOUBLE, and DOUBLE PRECISION are all variations on floating-point numbers. A floating-point number can handle either real numbers or irrational numbers (as well as whole numbers, of course). A real number is any number that can be represented in a fixed number of decimal
places, such as 1.25. An irrational number cannot be represented in a fixed number of decimal points. An example is 1/3, which is .333333… (to infinity). The database stores these numbers in scientific format. Single precision numbers (SINGLE or SINGLE PRECISION, depending on your database) are usually 4 bytes long. Double precision numbers are usually 8 bytes long, effectively making them able to handle a much larger range of numbers. Number Storage On The Database Although you and I represent numbers decimally—that is, using what is called base 10—computers store numbers in binary format using base 2. If a number is stored in 2 bytes, there are a total of 16 bits with possible values of 0 or 1. Therefore, the largest possible number of values that can be represented without some sort of encoding algorithm is 2 16 or 65,536. With signed numbers, one bit is reserved for the mantissa to indicate a negative or positive number, reducing the potential number of values to 2 15. Thus, a signed integer field stored in 2 bytes has a range of –32,768 to + 32,767. Even in an 8-byte field, there can only be 2 64 possible values. Computers use what is the known as the IEEE format to store floating-point numbers in scientific format to get around this limitation. Although this does not allow the storage of an infinite range of numbers, it does allow the computer to approximate very large and very small numbers with a high degree of accuracy. Scientific formats for numbers consist of three parts: the root, the letter E, and the exponent: 144.34267E+4. In this example, the exponent +4 indicates that the decimal point should be moved four places to the right: 1443426.7. An exponent of –4 would indicate that the decimal point should be moved four places to the left, yielding the number .014434267. The DOUBLE data type generally supports an exponent of plus or minus 308, which accommodates the storage of a very large or very small number in a compact manner. Date Data Dates are encoded on the database as numbers and are, therefore, limited in their range. Oracle’s DATE data type, for instance, has a range of 1 January, 4714 BC to 1 January, 4712 AD. The major RDBMSs are generally Year 2000 compliant. However, you should consider that your front-end development language might not support the same range of dates. Visual Basic, for instance, has a range of 1 January, 100 to 31 December, 9999. Inputting dates into the database can sometimes be a chore. The format of the date that the database expects is usually a startup option (that is, it is specified as an optional parameter when starting the database engine on the server). Usually, you can override this setting in an individual session by using the SET command. Oracle’s default date format is: INSERT INTO…
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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
Page 9 and 10: people checked each piece of code.
Page 11 and 12: and sell through your Web site. (Tr
Page 13 and 14: grammatical correctness. Kris offer
Page 15 and 16: In this chapter, I introduce the un
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Page 19 and 20: example, a “high-speed” Etherne
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Page 75 and 76: This example adds a column named Em
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Page 85 and 86: query result. (I expanded upon this
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Page 97 and 98: SELECT EMP_NO AS 'NUMBER', EMP_LNAM
Page 101 and 102: FROM EMPLOYEE The result is: MIN(EM
Page 103 and 104: GENEVIEVE WESLEY The LTRIM function
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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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nested transactions in an ODBCDirec
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wrkEmp.BeginTrans ' Start of inner
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Set User = object.CreateUser (name,
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three properties: Name, Password, a
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Database Type Specifier Example Mic
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QueryDef object and thus omits the
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this, specify a URL instead of a fi
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topic. Connection also has a Cancel
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docTemp.Properties.Append prpTemp d
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property is useful when two users m
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ForeignName property is set to the
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• The Primary property is a Boole
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' Display how many unique values th
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current object should be replicated
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"EMP_LNAME, EMP_SALARY FROM EMPLOYE
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set automatically reflects the chan
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workspaces. In a Jet workspace, BOF
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each record in the RecordSet. The c
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occurrences. FindLast finds the las
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Products | Contact Us | About Us |
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chapter provides an example of usin
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End Sub Table 5.15 Constants for th
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loaded as it does in DAO, and RDO p
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doEngine object is created. Additio
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messages (ODBC SQL_SUCCESS_WITH_INF
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Previous Table of Contents Next Pro
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in an rdoEnvironment object, all rd
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If cSalary !emp_Salary Then ' If c
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password parameters are not supplie
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The rdoConnections Collection And r
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Command1(0).Enabled = True Command1
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Dim vErr As rdoError For Each vErr
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objects. If the query was successfu
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embrace where two processes lock ea
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Connect:="UID=Coriolis;PWD=Coriolis
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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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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
show all

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