SQLSelect Class

Object
  DataServer
    SQLSelect
      SQLCatalogQuery
      SQLTable

 CLASS SQLSelect INHERIT DataServer

public class SQLSelect : DataServer

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	Name	Description
	SQLSelect	Construct a SQL select object.

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	Name	Description
	AppendData
	AppendFlag	Missing documentation
	BoF	A logical value indicating whether the server is positioned at the beginning of the result set, on the first row. (Overrides BoF.)
	BoundedColumns	Missing documentation
	Clients	Missing documentation (Inherited from DataServer.)
	ConcurrencyControl	A constant, identifying the mode of automatic concurrency control for this data server, determining when and how records are locked and released: (Inherited from DataServer.)
	Connection	The SQL connection object that the SQLSelect is using to manipulate the result set.
	CursorName	A string containing the cursor name.
	CursorType	A constant, which describes the cursor type used by the SQL statement:
	DBStruct	An array containing the structure of this data server. (Overrides DBStruct.)
	Deleted	A logical value indicating whether the current row has been deleted.
	EoF	A logical value indicating whether the server is positioned at the end of the result set, after the last row. (Overrides EoF.)
	ErrInfo	An SQLErrorInformation object.
	FCount	The number of columns in the result set. A value of -1 indicates an error. (Overrides FCount.)
	FOUND	A logical value indicating whether the previous search operation succeeded.
	HLStatus	Missing documentation (Inherited from DataServer.)
	HyperLabel	The hyperlabel connected to this data server. From the hyperlabel, you can retrieve additional information about the data server (Inherited from DataServer.)
	IndexColumns
	LASTREC	Missing documentation
	Modified
	MoreResults	A logical value representing whether there are more rows to retrieve.
	Name	A string representing the name of this data server. (Inherited from DataServer.)
	NameSym	A symbol representing the name of this data server. (Inherited from DataServer.)
	NativeSQL	A string containing the native SQL text of the statement. Level 2
	NullAsBlank	A logical value determining whether SQL NULL values are strongly typed (TRUE) or not (FALSE, default value).
	NumCols
	NumParameters	A numeric value containing the number of parameters. A value of -1 indicates an error. Level 2
	NumResultColumns	A numeric value containing the number of columns in the result set.
	NumSuccessfulRows	A numeric value containing the number of rows that were modified by a delete, append, or update operation.
	PrepFlag	A logical value that indicates if the select statement has been prepared.
	RecCount	A numeric value representing the number of rows in the data server. (Overrides RecCount.)
	Recno	A numeric value representing the relative position in the data server. (Overrides RecNo.)
	RecNo	A numeric value representing the current record number, identifying the position of the record pointer in this data server. (Inherited from DataServer.)
	RowCount
	ScrollConcurrency	A constant, which describes the concurrency mode used by the SQL statement:
	ScrollUpdateType	A constant, which describes the type of SQL statement to use during append, update or delete operations.
	SimulateCursor	A constant, which describes the way the ODBC drivers tries to guarantee that update or delete statements only affect one single row.
	SQLColumns	Missing documentation
	SqlData	Missing documentation
	SQLString	A string representing the SQL statement text.
	Statement	A SQL statement object.
	StatementHandle	A numeric value representing the statement handle.
	Status	A hyperlabel object identifying the status after the last operation. (Overrides Status.)
	TableName	A string representing the name of the table.
	TimeStampAsDate	Missing documentation
	Used	A logical value indicating whether the current query is active. It returns TRUE if the current query is active; otherwise, it returns FALSE.

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	Name	Description
	AddDateVal
	AddTimeString
	Append	Create a blank row in the buffer; this blank row becomes the current position and is ready for assignment of data values. The SQLSelect:RecNo of this buffer is SQLSelect:RecCount+1. (Overrides Append.)
	AppendRow	Insert the row that has been created in the buffer since the last SQLSelect:Append() operation.
	AsString	Return the descriptive label defined for this data server. (Inherited from DataServer.)
	BindColumn
	Close	Close the cursor corresponding to the server. Note that the database connection is not closed, only the cursor. (Overrides Close.)
	Column	Return a specified SQL column.
	ColumnAttributes	Return the SQL column attributes for a specified column.
	Commit	Save the changes (updates and deletes) made since the last Commit(). (Overrides Commit.)
	DataField	Return the data (DataField object) at a specified column position. (Overrides DataField(Usual).)
	Delete	Delete the current row. (Overrides Delete.)
	DirectSkip
	Error	Provide a method for handling error conditions raised during database processing. This is an event handler: it is automatically called by other methods; the developer does not normally need to call the error method, but might want to replace or amend it.
	Execute	Open the cursor.
	ExtendedFetch	Provide extended fetch capabilities, specifying type and row.
	Fetch	Fetch the next row.
	FIELDGET	Retrieve the contents of the specified column. (Overrides FIELDGET(Usual).)
	FieldGetFormatted	Retrieve the contents of the specified column according to the formatting specifications of its field specification. (Overrides FieldGetFormatted(Usual).)
	FieldHyperLabel	Return the hyperlabel of a specified column. (Overrides FieldHyperLabel(Usual).)
	FieldInfo	Retrieve information about or set an alias for the indicated column.
	FieldName	Return the name of a specified column. Note that the column's hyperlabel also contains a name. (Overrides FieldName(Usual).)
	FieldPos	Return the position of a specified column within the data server, as a number starting with 1. (Overrides FieldPos(Usual).)
	FIELDPUT	Assign a value to a column in a data server. (Overrides FIELDPUT(Usual, Usual).)
	FieldSpec	Return the field specification object for the indicated column. (Overrides FieldSpec(Usual).)
	FieldStatus	Return a hyperlabel object identifying the status after the last operation. (Overrides FieldStatus(Usual).)
	FieldSym	Return the symbolic name of a specified column. Note that the column's hyperlabel also contains a name; these two names are the same in the code generated by the SQL Editor. (Overrides FieldSym(Usual).)
	FieldValidate	Validate the provided value according to the validation rules of the indicated column's FieldSpec. (Overrides FieldValidate(Usual, Usual).)
	FLOCK	This method is provided to override the inherited functionality from the DataServer class, as it does not apply to SQLSelect. (Overrides FLOCK.)
	FreeStmt	Free the statement, according to the specified option.
	GetData	Retrieve the contents of the specified column.
	GetdateVal
	GetLookupTable	Retrieve a two-column array of values from two fields in the server.
	GetStatementOption	Retrieve the current setting for a statement option.
	GetTimeStamp
	GetTimeString
	GoBottom	Position the data server on the last row. (Overrides GoBottom.)
	GoTo	Position the data server on the specified row number. (Overrides GoTo(Usual).)
	GoTop	Position the data server on the first row. (Overrides GoTop.)
	NoIVarGet	Provide a general error interception that is automatically called (in any class) whenever an access reference is made to a non-existent exported instance variable. In the SQLSelect class, it is used to implement the virtual column variable. Important! NoIVarGet() should not be called directly; it is called by the system for handling invalid references. (Overrides NoIVarGet(Usual).)
	NoIVarPut	Provide a general error interception that is automatically called (in any class) whenever an assignment reference is made to a non-existent exported instance variable. Important! NoIVarPut() should not be called directly; it is called by the system for handling invalid references. (Overrides NoIVarPut(Usual, Usual).)
	Notify	Provide a method that is automatically called by the action methods of the server after completion of some significant event: a column has changed, the server position has changed, some operation has been completed. Its standard implementation is to broadcast the same notification to its attached clients. (Overrides Notify(Usual, Usual).)
	NumResultCols	Return the number of columns in the result set.
	PostInit	Implement customized initialization code for the window. (Inherited from DataServer.)
	PreExecute	Return the SQL command that is generated by X#.
	PreInit	Implement customized initialization code for the server. (Inherited from DataServer.)
	Prepare	Prepare the statement.
	Refresh	Refresh the current row in the buffer, discarding any changes that have been made.
	RegisterClient	Register an object as a client of this data server, so that it receives notification messages from the server about certain actions. (Inherited from DataServer.)
	ReReadRow
	ResetCursor
	ResetNotification	Resume the broadcasting of Notify messages to the server's attached clients (after SQLSelect:SuspendNotification() has been called). (Overrides ResetNotification.)
	RLOCK	This method is provided to override the inherited functionality from the DataServer class, as it does not apply to SQLSelect. (Overrides RLOCK(Usual).)
	RLockVerify	This method is provided to override the inherited functionality from the DataServer class, as it does not apply to SQLSelect. (Overrides RLockVerify.)
	Rollback	(Overrides Rollback.)
	Seek	Move to the next record having a specified key value in the controlling order. (Inherited from DataServer.)
	SetColumnAttributes
	SetDataField	(Overrides SetDataField(Usual, Usual).)
	SetPos
	SetPrimaryKey	Specify a column to be used as a unique index in searched updates or deletes that require a key (i.e., SQLSelect:ScrollUpdateType = SQL_SC_UPD_KEY).
	SetStatementOption	Change a statement option.
	SetTimeStamp
	Skip	Move forward or backward relative to the current row. (Similar to the Skip() function). (Overrides Skip(Usual).)
	SuspendNotification	Suspend the broadcasting of Notify messages to the server's attached clients. (Overrides SuspendNotification.)
	Unlock	This method is provided to override the inherited functionality from the DataServer class, as it does not apply to SQLSelect.
	UnLock	Remove all locks held on this data server. (Inherited from DataServer.)
	UnRegisterClient	Remove the registration of an object as a client of this data server, so that it no longer receives notification messages from the server about certain actions. (Inherited from DataServer.)
	Update	Update this server with data from another server or table. (Inherited from DataServer.)
	Update(Usual)	Update the current row or restore the original values of the row.
	UpdateCursor
	UpdateKey
	UpdateVal

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Once a SQL table is opened in a DataServer object, it can be manipulated through the methods of the SQLSelect class:

X#

Copy

1oCust:= SQLSelect{"SELECT * FROM customer"}
2oCust:Skip(3)
3? oCust:CustName
4oCust:Delete()
5oCust:Close()

The model for SQL returns rows and columns as a result set, instead of records and fields. The columns can be considered as exported instance variables of the object. They can also be accessed through the FieldGet() and FieldPut() methods, with the column identified through a symbol, a string, or a number:

X#

Copy

1oCust := SQLSelect{"SELECT * FROM customer"}
2oCust:CustNo := 1234
3? oCust:CustNo
4oCust:FieldPut(#CustNo, 1234)
5oCust:FieldPut("CustNo", 1234)
6oCust:FieldPut(1, 1234)
7? oCust:FieldGet(#CustNo)
8? oCust:FieldGet("CustNo")
9? oCust:FieldGet(1)

(The columns are, of course, not real exported variables of the SQLSelect class. See "Objects, Classes, and Methods" in the Programmer's Guide for a discussion of how these "virtual" exported variables are created using the NoIVarGet() and NoIVarPut() methods.) Unlike the DBServer class, the SQLSelect class does not position the server on the first row when an object is created. However, when a method that references the first row is called, it will automatically be positioned on the first row. For databases that support positioned operations (such as, WATCOM) using scrollable cursors, the positioning methods (GoTop(), GoBottom(), Skip(), GoTo()) use the driver. Otherwise, SQLSelect buffers the rows as it moves forward and performs the positioning methods by moving within the buffer (for backwards positioning). Refer to the SQLConnection:ScrollCsr access for additional information. To disable this buffering, use the SQLSelect:BufferData() method. It is not possible to use the SQLSelect class to create a database table; the table must exist before a server can be opened on it.

Tip
The cursor type and lock mode that is used by a SQLSelect object can be controlled by the following functions. Please consult the documentation for the ODBC driver you are using to see the effects of this setting on the performance of your application. SqlSetStmtConcurrency(), SqlSetStmtCursorType(), SqlSetStmtSimulateCursor()

Reference

VO Namespace