Tài liệu Oracle Unleashed- P22 pdf

The methods of the Database object are used to retrieve results, apply SQL transactions, and call stored procedures. In most cases, the application should declare one Database object globally. The primary means of retrieving results from an ODBC data source is the Snapshot object. The Snapshot object is created using the CreateSnapshot method of the Database object. The CreateSnapshot method takes two arguments: a SQL SELECT statement, and a numeric constant used to control processing of the SQL. Unless the application needs to be portable to different RDBMSs, this numeric constant should be set to DB_SQLPASSTHROUGH, (64), which sends the statement directly to the server for processing. This mode allows the developer to use the native syntax of the RDBMS, and prevents the local Microsoft Access engine from attempting to parse and process the SQL. The following code fragment provides a simple example of the use of the CreateSnapshot method: Dim dsContacts As Snapshot Set dsContacts = dbOracle.CreateSnapshot("SELECT a.last_name, a. first_name, b.phone_nbr FROM individual a, phone b WHERE a.ID = b.IndividualID(+) ORDER BY 1, 2", DB_SQLPASSTHROUGH) The example assumes that the Database object has already connected to the data source. Note that if DB_SQLPASSTHROUGH is not specified, a syntax error results because the local Access engine attempts to parse the SQL and does not recognize the outer join syntax. After applying the SQL and creating the result set, there are numerous methods that can be applied to position the record pointer in the cursor. The MoveFirst, MoveLast, MoveNext, and MovePrevious methods are the most commonly used, and their purposes should be self-explanatory. Visual Basic provides the additional method FindFirst to position the record pointer at the first record matching specific criteria. For example, assuming that the record pointer is positioned at the first record, the following line would find the first individual with the last name Smith, based on the result set returned by the previous example: dsContacts.FindFirst("last_name = 'Smith'") The criteria supplied as the argument to FindFirst are syntactically equivalent to a WHERE clause in SQL. The additional methods FindNext, FindPrevious, and FindLast operate on the same basis. After positioning the record pointer, an application can assign variables to result set column values using the Fields property of the Snapshot. The Fields collection is simply a representation of the columns in the result set. They can be accessed by name or by a zero-based index, starting with the left-most column. Listing C.2 demonstrates methods for assigning application variables to result set data. Listing C.2. The Fields collection is used to access result set data. Dim iRow As Long iRow = 0 dsContacts.MoveFirst While Not dsContacts.EOF ReDim Preserve szLast(iRow) As String ReDim Preserve szFirst(iRow) As String ReDim Preserve szPhone(iRow) As String Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. szLast(iRow) = dsContacts.Fields("last_name").Value szFirst(iRow) = dsContacts.Fields(1).Value szPhone(iRow) = dsContacts.Fields("phone_nbr").Value dsContacts.MoveNext Wend dsContacts.Close When assigning values from the Fields collection to variables, the application should always check for null values, as below: If (IsNull(dsContacts.Fields("last_name")) = False) Then szLast(iRow) = dsContacts.Fields("last_name").Value End If Assigning a null value to an application variable will produce a run-time error. As evident from listing C.2, the more readable form of accessing the fields collection is to access them by name. When there are only a few columns in the result set, this point does not seem significant. However, if there are twenty or thirty columns in the result, it becomes very difficult to identify a column by index. Also, any changes to the SQL which created the result set may cause the indexes to reference different columns. While it may save a few keystrokes to use numeric indexes, in the interest of writing maintainable code, the fields collection should be accessed by column name whenever possible. When the columns of the result set are not static at design-time, the Count property of the Fields collection can be used to determine the number of columns, and the Name property , (which applies to each individual field), can be used to create column headings. A single Visual Basic object, such as a Database or Snapshot object, cannot be passed as a parameter to a function, but an array of objects can. When dealing with single object, it can be declared as a single element array so that it can be passed to functions and subroutines, and generic methods can be written to operate on these objects. While Visual Basic also provides Dynaset, Table, and QueryDef objects for retrieving result sets, these objects are not commonly used to communicate with ODBC data sources. The primary difference between a Snapshot and the Dynaset and Table objects in ODBC environments is that the Snapshot creates a read-only result set, while the Dynaset and Table objects' result sets can be edited. However, these objects should not be used for database transactions, for reasons that will be discussed next. The Dynaset is similar to the Snapshot, except that its result set is refreshed every time a change is made to one of its underlying tables. This is true only for local database files. With ODBC connections, the Dynaset object is, in essence, identical to the Snapshot object, except that the Dynaset can be used for in-place updates, deletes, and insertions. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. While Table objects could be used by applications accessing ODBC data sources, it would be unacceptable to do so in most situations. Using the OpenTable method is not as readable as a SELECT statement in which the columns are clearly identified and referenced by name, and when accessing Oracle, the Table object is the equivalent of a Dynaset created with the SQL SELECT * FROM table_name. In both cases, the column list is expanded, and the statement is sent to the server using the API function SQLExecDirect(). A QueryDef object is similar to a view that is created and stored by the application. The QueryDef object simply stores frequently used SQL so that it can be read from the database and executed as needed. QueryDefs cannot be created over ODBC connections. Views are a better alternative, because they are stored in the database with a bound access plan, and the SQL does not need to be executed from the client application. The Visual Basic DataControl provides another option for retrieving a result set through ODBC. The DataControl is used to bind controls to result set columns. To retrieve a result set using a DataControl, its Connect property must be set to the full connect string, as previously described for the OpenDatabase method. This property can be set at run-time using a statement like the one below: Data1.Connect=szConnect This example assumes that szConnect was constructed as in Listing C.1. The RecordSource property of the DataControl is used to retrieve the result set. If this property is set at design-time, results will be retrieved as soon as the Connect property is assigned and a connection is established. If the Connect property is also assigned at design-time, results will be fetched when the object is instantiated. The RecordSource property can consist of a table name, view name, or a SELECT statement. The DB_SQLPASSTHROUGH option is not available to the DataControl, so if a SELECT statement is used as the RecordSource property, it may not contain an outer join or any other Oracle-specific syntax. In order to use a DataControl with a complex SELECT statement, a view should be created so the DataControl can simply use the view as the data source. Controls can be bound to result set columns through the DataControl. A text box, for example, can be bound to a DataControl by setting its RecordSource property to the name of the DataControl and setting its DataField property to the name of the column in the result set that it should contain. When the result set is retrieved, the text box is then automatically populated with the value of the specified column at the current record position. Numerous third-party vendors provide custom controls that can be bound to result sets in this manner. The standard controls that can be bound to a result set through the DataControl are limited to text boxes, checkboxes, labels, images, and picture boxes. The Recordset property of the DataControl is nearly identical to a Dynaset object. The MoveFirst method and other positioning methods apply to the Recordset property of the DataControl, as well as the BOF and EOF properties, and the Fields collection. Consequently, the DataControl's result set can be accessed programmatically, in addition to being accessed by bound controls. Using bound controls is generally not the best approach to developing client/server applications, however. The nature of bound controls requires that the cursor to which they are bound persists for the life of the bound controls. For most applications, it is preferable to read the data, populate the necessary controls programmatically, and close the cursor. Note that in Listing C.2, the Snapshot object is used to populate a Visual Basic array, and then it is immediately closed, thereby freeing the cursor on the server. In heavily used systems with a large number of clients, this can have a significant impact on performance. While the DataControl can be used to perform inserts as well as in-place updates and deletions, it is strongly recommended to use these methods through ODBC. Unfortunately, when Visual Basic establishes an ODBC connection, the ODBC AutoCommit connection option is enabled, and Visual Basic does not provide a method to disable this option. As a result, transaction control is not possible. Even if the transaction involves only a single table and a single operation, the DataControl is a bad choice for applying transactions. The DataControl always updates every column. If there are unbound columns, these values must be set manually, which complicates the entire process. For example, if an application needs to supply a transaction timestamp with every update, there is no clean way to do this. The DataControl does not support passthrough mode, so the Oracle system variable, sysdate, cannot be supplied as a value. The application has to supply a time based on the local workstation's clock, which would not only require an assignment to a member of the Fields collection, it would almost certainly introduce inaccuracies. These same problems apply to the Dynaset and Table objects because they use the same methods for applying transactions. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. There are three possible solutions to overcome the AutoCommit problem. One solution would be to use Oracle stored procedures exclusively for transaction processing. The ExecuteSQL method of the Database object can be used to call Oracle stored procedures, providing an easy and safe way to communicate transactions to the database. Using stored procedures also simplifies the development of the client application, by freeing it from the responsibility of generating dynamic SQL and controlling transactions. The ExecuteSQL method requires a single argument. The argument is a text string of the SQL to be executed. This method uses passthrough mode by default, so any SQL that can be evaluated by Oracle can be supplied, including the ODBC syntax for calling Oracle procedures. Listing C.3 demonstrates the use of the ExecuteSQL method to call an Oracle stored procedure. Listing C.3. The ExecuteSQL method can be used to call Oracle stored procedures. Dim iRows As Integer Dim szStmt As String szStmt = "{call insert_individual('" & txtLastName.Text & ", '" szStmt = szStmt & txtFirstName.Text & ", '" & txtNotes.Text szStmt = szStmt & ", '" & txtDateOfBirth.Text & "')}" iRows = dbOracle.ExecuteSQL(szStmt) The ExecuteSQL method returns the number of rows affected by the transaction, and this value can be tested to determine the success or failure of the operation. Unfortunately, because Visual Basic does not support prepared execution of SQL statements, it cannot call Oracle stored procedures that use output parameters, or add parameters to the procedure call. The statement must be built dynamically, as in Listing C.3. A second possible means of overcoming the AutoCommit problem is to use a third-party product, such as Oracle Objects for OLE. This product provides direct replacements for the Visual Basic objects and methods for communicating with Oracle databases. For example, the following code fragment establishes an Oracle session through VB that can be used for transaction control: Dim Session As Object Dim dbOracle As Object Set Session = CreateObject("OracleInProcServer.XOraSession") Set dbOracle = Session.OpenDatabase("ORACLE", "scotty/tiger", 0&) The preceding example uses the Visual Basic generic (OLE) Object data type and the CreateObject function to request a new XOraSession object from Oracle's OLE server. The methods of the Session object can then be used to create other objects, and to manage transactions, using the BeginTrans, CommitTrans, and Rollback methods. A full discussion of the features of Oracle Objects for OLE is beyond the scope of this appendix. However, it is important to note that it can provide Visual Basic applications with the capability to control transactions, add parameters to SQL and procedure calls, and make use of output parameters when accessing Oracle databases, among other things. The potential shortcoming of the previous two means of bypassing Visual Basic's AutoCommit behavior is that they are not portable. If a client application needs to access different RDBMSs, these solutions may not be feasible. A third approach to overcoming the AutoCommit problem is to use the ODBC API directly, which opens numerous possibilities, including the creation of a truly portable client application. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. A small subset of the ODBC API can be used to provide transaction control in Visual Basic applications accessing ODBC data sources. The declarations in Listing C.4 should be placed in a module, and will provide access to all functions needed to connect, apply transactions through embedded SQL, and rollback or commit them, as needed. Listing C.4. ODBC API declarations for Visual Basic. Declare Function SQLAllocConnect Lib "odbc.dll" ( ByVal hEnv As Long, hDBc As Long) As Integer Declare Function SQLAllocEnv Lib "odbc.dll" ( hEnv As Long) As Integer Declare Function SQLAllocStmt Lib "odbc.dll" ( ByVal hDBc As Long, hStmt As Long) As Integer Declare Function SQLDisconnect Lib "odbc.dll" ( ByVal hDBc As Long) As Integer Declare Function SQLDriverConnect Lib "odbc.dll" ( ByVal hDBc As Long, ByVal hWnd As Integer, ByVal szCSin As String, ByVal cbCSin As Integer, ByVal szCSOut As String, ByVal cbCSMax As Integer, cbCSOut As Integer, ByVal f As Integer) As Integer Declare Function SQLExecDirect Lib "odbc.dll" ( ByVal hStmt As Long, ByVal SQLString As String, ByVal SQLStringLen As Long) As Integer Declare Function SQLFreeConnect Lib "odbc.dll" ( ByVal hDBc As Long) As Integer Declare Function SQLFreeEnv Lib "odbc.dll" ( ByVal hEnv As Long) As Integer Declare Function SQLFreeStmt Lib "odbc.dll" (ByVal hStmt As Long, ByVal EndOption As Integer) As Integer Declare Function SQLSetConnectOption Lib "odbc.dll" ( ByVal hDBc As Long, ByVal fOption As Integer, ByVal vParam As Long) As Integer Declare Function SQLTransact Lib "odbc.dll" ( Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. ByVal hEnv As Long, ByVal hDBc As Long, ByVal fnType As Integer) As Integer Global Const SQL_NTS = 3 Global Const SQL_DRIVER_NOPROMPT = 0 Global Const SQL_COMMIT = 0 Global Const SQL_ROLLBACK = 1 Global Const SQL_MAX_MESSAGE_LENGTH = 512 Global Const SQL_AUTOCOMMIT = 102 Global Const SQL_DROP = 1 After establishing a connection for retrieving results with the OpenDatabase method, the application should establish a second connection to the database using the API functions—for applying transactions. After establishing this connection, SQLSetConnectOption() should be used to disable AutoCommit. Listing C.5 demonstrates how this might be accomplished. Listing C.5. Establishing a database connection using the ODBC API. Dim hEnv As Long Dim hDBc As Long Dim szConnectString As String Dim iError As Integer Dim hWnd As Integer Dim iLenCSOut As Integer Dim szCSOut As String * 254 szConnectString = "ODBC;DSN=ORACLE;UID=scotty;PWD=tiger;" hWnd = frmMDIFrame.hWnd ' Allocate environment iError = SQLAllocEnv(hEnv) ' Allocate connection iError = SQLAllocConnect(hEnv, hDBc) ' Load driver & connect to ODBC data source iError = SQLDriverConnect(hDBc, hWnd, szConnectString, SQL_NTS, szCSOut, 254, iLenCSOut, SQL_DRIVER_NOPROMPT) Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. ' Disable autocommit iError = SQLSetConnectOption(hDB, SQL_AUTOCOMMIT, 0) Obviously, in practice, the connect string would not be hard-coded and the return value of each function should be checked. The example in Listing C.5 is intended only to demonstrate the use of the ODBC API to establish a database connection. Once a connection has been established, the application can apply transactions using SQLExecDirect() after allocating a statement handle with SQLAllocStmt(). SQLTransact() can then be used to commit or rollback a transaction based on the return value of SQLExecDirect(). After applying the transaction, the application should call SQLFreeStmt() to free the resources allocated to the statement handle. Listing C.6 provides an example of the calls to these functions. Listing C.6. Applying a transaction using embedded SQL. Dim hStmt As Long ' Allocate a statement handle iError = SQLAllocStmt(hDBc, hStmt) For i = 0 To iStmts ' Apply SQL iError = SQLExecDirect(hStmt, szSQL(i), SQL_NTS) If iError Then ' Rollback iNextErr = SQLTransact(hEnv, hDB, SQL_ROLLBACK) Exit For End If 71501,2744Next i If (iError = 0) Then ' Commit iError = SQLTransact(hEnv, hDB, SQL_COMMIT) End If ' Free the statement handle iError = SQLFreeStmt(hStmt, SQL_DROP) The example in Listing C.6 assumes that the environment and connection handle, hEnv and hDBc, are valid and connected to the data source, and that szSQL is an array of iStmts SQL statements. If any statement in the transaction fails, a rollback is issued and processing of the transaction is discontinued. If all statements are processed without errors, the entire transaction is committed. Regardless of whether the transaction is committed or rolled back, the application Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. frees the statement handle. When the application exits, it needs to disconnect from the data source and free all resources allocated to the environment and connection handles. This can be accomplished with three functions calls, as illustrated in the following lines: iError = SQLDisconnect(hDB) iError = SQLFreeConnect(hDB) iError = SQLFreeEnv(hEnv) The full capabilities of ODBC are far beyond the scope of this discussion, but many additional capabilities can be provided, and an application can be constructed in a manner that is completely database-independent using embedded SQL. However, if an application does not need to be portable to other database platforms, it may be easier to use stored procedures or a third-party product, such as Oracle Objects for OLE, to apply transactions from Visual Basic. It is unfortunate that Visual Basic does not provide a means by which AutoCommit can be disabled for connections established internally. This is a limitation of the implementation of the Jet Database Engine that Visual Basic uses. One of the most powerful, (and potentially dangerous), features of Visual Basic is the means by which errors are trapped, using the On Error statement. This statement is well-used in Visual Basic programming because all untrapped run-time errors are fatal. The On Error statement is used to specify an error handler to which execution jumps if an error occurs. The error handler can be specified using GoTo, or Resume Next can be specified to allow program execution to continue normally. The system variables Err and Error$ store a numeric code and a text description for the error that occurred most recently. The fact that only the most recent value is stored is what makes On Error Resume Next a somewhat dangerous way to trap and handle errors. It is very convenient to use, but the value of Err should be checked wherever an error requiring a specific action occurs. A common mistake in Visual Basic programming is to misunderstand its array dimensions. Consider the following declaration, for example: ReDim szStrings(2) As String Most would assume that this declares an array of two strings. However, the previous statement actually allocates an array of three strings. The subscript in an array declaration sets the upper bound, not the number of elements in the array, so szString(0), szString(1), and szString(2) are all valid, based on the declaration. The base subscript can be changed to 1, using the Option Base statement: Option Base 1 If this statement appears in the same module as the previous array declaration, the array would have only two elements, szString(1) and szString(2). In this case, szString(0) would be an invalid reference. Summary The Visual Basic programming language is particularly easy to learn and use. Nearly all developers have some experience with BASIC, and many of the language constructs have been in place since the very first versions of what is now referred to as BASIC A. Despite some idiosyncrasies, a lack of object-oriented features, and relatively weak database support, Visual Basic is an extremely useful development tool. Its shortcomings are offset by the simplicity of its IDE and language, and extensive third-party support. The uncluttered and completely non-modal IDE, a flexible ANSI-standard programming language, Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. and a wide variety of pre-built objects make Visual Basic an excellent choice for projects requiring rapid development. Previous Page TOC Next Page Home Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Previous Page TOC Next Page Home ● D ❍ Using Delphi ■ Configuring a Data Source ■ Communicating with the Database ■ Summary D Using Delphi Borland's Delphi is one of the newest visual development tools for Microsoft Windows. It has positioned itself in the market as a high performance alternative to Microsoft Visual Basic. What separates Delphi from its competition in this regard is its ability to compile stand-alone executables and .DLLs, with no run-time libraries required. Delphi provides full support of ODBC and numerous object classes for communicating with ODBC data sources. It ships with a single-user desktop version of Borland's InterBase Server and its ODBC-enabled ReportSmith querying and reporting tool. The client/server edition also ships native IDAPI drivers for Oracle, Sybase, and Informix, among others. Object Pascal, the programming language used in Delphi development, supports many of the object-oriented features typically associated with C++, including public and private data members and functions, inheritance, and polymorphism. The language also supports a wide range of data types and advanced features, including true pointer types and structured exception handling. While Object Pascal and Delphi provide an abundance of noteworthy features, this appendix focuses primarily on Delphi's support for database applications. An overview of the more significant features of the language is included, as well as a brief discussion of the strengths and weaknesses of Delphi. Configuring a Data Source To make a data source available to Delphi, IDAPI.CFG must be edited using the BDE configuration utility. This utility can be accessed from the Tools menu in the IDE. When the utility is started, it displays currently configured data sources, some of which may be pre-configured IDAPI interfaces, depending on the options selected when Delphi was installed. The main window of the BDE configuration utility should appear as shown in Figure D.1. Figure D.1. The main window of the Delphi BDE configuration utility. Delphi can interface with any ODBC data source configured and defined in ODBC.INI. To configure an existing ODBC data source for Delphi's use, click on the New ODBC Driver command button. A simple dialog box displays and requires three basic items. The SQL Link Driver name is simply an identifier to be used by Delphi, and any unique name can be used. Using the Default ODBC Driver drop-down, select from the list of currently installed drivers. If the required driver does not appear in the list, it has not been correctly installed. ODBC drivers can be installed using ODBCADMN. EXE, a Microsoft utility that is typically provided by driver vendors. After selecting a driver, the Default Data Source Name drop-down will be populated with a list of the data sources defined for the selected driver. Figure D.2 provides an example of how this dialog box might look when configuring the Oracle7 ODBC driver. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. [...]... choice for developing client applications to interface with Oracle Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Previous TOC Page Next Page Home Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Previous TOC Page q Next Page Home E r Oracle Power Objects Programming Reference s Overview of Oracle Basic s Supported Data Types s Variables s Constants... (LAST_NAME, FIRST_NAME) '); Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark qryAddCust.SQL.Add('VALUES (:Last, :First)'); qryAddCust.Prepare; {this code can be executed many times} dbOracle.StartTransaction; qryAddCust.Params[0].AsString(txtLast.Text); qryAddCust.Params[1].AsString(txtFirst.Text); try qryAddCust.ExecSQL; dbOracle.Commit; except dbOracle.Rollback; end; The ExecSQL... widest developer experience and level This chapter discusses the majority of all commands and functions comprising Oracle Basic in order to provide you with a reference on syntax and purpose Overview of Oracle Basic Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Oracle Basic is fully compatible with ANSI BASIC and is therefore compatible with Microsoft Visual Basic You are... Functions s String Functions s Test Functions s User Dialog Functions s Summary E Oracle Power Objects Programming Reference Power Objects uses Oracle Basic as its programming language Oracle Basic is fully compatible with ANSI BASIC with the additions of object concept extensions and Structured Query Language (SQL) extensions Oracle chose Basic as the programming language in order to appeal to the widest... of databases Blaze Oracle7 SQL Server CHAR CHAR BINARY DATE DATE BIT FLOAT FLOAT CHAR INTEGER LONG DATETIME LONG LONG RAW FLOAT LONG RAW MLSLABEL IMAGE MLSLABEL NUMBER INT NUMBER ROWID MONEY ROWID VARCHAR REAL VARCHAR VARCHAR2 SMALLDATETIME VARCHAR2 SMALLINT SYSDATE Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark TEXT TIMESTAMP TINYINT VARBINARY VARCHAR Oracle Basic-related... object) There are eight types of Oracle Basic variables that you can declare: Integer, Long, Single, Double, Date, String, Object, and Variant For a more in-depth understanding of data types, please refer to the Oracle Power Objects online help under the following search concepts: data types – Oracle Basic, column data types, and column data types by database Variables Oracle Basic variables are names... data type 3 RecDty_Long Long data type Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark 4 RecDty_Double 6 RecDty_Date Double data type Date data type Power Objects also has a large number of reserved words Reserved words are not case sensitive Reserved words include words from ANSI standards, Oracle SQL standards, and Oracle Basic Each of the lists of reserved words is well... is well documented under the search concepts in the online help as follows: reserved words – Oracle and reserved words – Oracle Power Objects Operators Operators are the verbs in the Oracle Basic statements that enable a developer to create and evaluate expressions involving variables of various data types Oracle Basic operators include arithmetic, string, comparison, logical, date, assignment, and... in decimal notation For more information on Oracle Basic expression, refer to the search concept expressions and the subtopic Expressions in Oracle Basic in the online help Statements The three types of Oracle Basic statements are comment, assignment, and command The comment statement begins either with a single apostrophe (') followed by text or with the Oracle Basic reserved word REM (stands for remark)... variable or object property followed by Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark an equal sign (=) and an expression The command statement is any valid use of an Oracle Basic command or reference to an object method, subroutine, or function A function returns a value, but the value does not have to be assigned Most Oracle Basic statements are represented one statement . interface with Oracle. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Previous Page TOC Next Page Home Please purchase PDF Split-Merge. comprising Oracle Basic in order to provide you with a reference on syntax and purpose. Overview of Oracle Basic Please purchase PDF Split-Merge on www.verypdf.com