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SQLDBC::SQLDBC_ResultSet Class Reference

#include <SQLDBC.h>

Inheritance diagram for SQLDBC::SQLDBC_ResultSet:

SQLDBC::SQLDBC_ConnectionItem List of all members.

Detailed Description

A class for presenting a database result set.

A database result set is generated by executing an SQL statement that queries the database.

Select statments, catalog functions, and some procedures create result sets. For example, the following SQL statement creates a result set containing all the rows and columns of the table DUAL:

SELECT * FROM DUAL

A result set can be empty, which is different from there being no result set at all. For example, the following SQL statement creates an empty result set:

SELECT * FROM DUAL WHERE 1 = 2

An SQLDBC_ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next() method moves the cursor to the next row, and as it returns SQLDBC_NO_DATA_FOUND when there are no more rows in the SQLDBC_ResultSet object, it can be used in a WHILE loop to iterate the result set.

Example for creating an SQLDBC_ResultSet object:

SQLDBC_Statement *stmt = conn->createStatement ();
stmt->execute ("SELECT * FROM DUAL");
SQLDBC_ResultSet *rs = stmt->getResultSet ();
rs->next();

To reduce the time needed for retrieving the data from the database, the SQLDBC_ResultSet class supports so called block cursors, which can return more than one row at a time. The rows returned by a block cursor are called a 'row set'. The result set is fixed, the rowset is not. It changes position and contents each time a new set of rows is retrieved from the database.

With block cursors, the method setRowSetSize() nust be used with a parameter greater than 1.

Navigation within the data represented by the SQLDBC_ResultSet object is possible using of navigation methods like first(), next(), previous(), relative() etc.

When block cursors are used, after applying the navigation methods, the cursor points to the actual row set. For example assuming a result set size of 50 and a rowset size of 10, in the following sequence the block cursor points to the rows indicated:

In order to perform operations that operate on a single row only when multiple rows have been fetched, the application must indicate which row is the current row. When a block cursor first returns a row set, the current row is the first row of that row set. To change the current row, the application must call the member function setPos().

The data of a certain column in the current row can be retrieved by calling the method getObject().

Data fetched from the database is passed on to the application in variables that the application has allocated for this purpose. Before fetching the data from the database, the application bind these variables to the columns of the result set. Applications can bind any number of columns of the result set, including binding no columns at all.

Binding of columns is done by calling to the member function bindColumn(). The column binding valid for all rows.

After positioning the cursor through navigation methods, the data from the database is written into the bound column variables by a call to the member function fillRowSet(). When block cursors are used, the number of rows actually filled can be determined with the member function getResultCount().

For unbounded columns, data can be written into application variables with getObject(), or - in case of block cursors - by calling setPos() on the rowset and then calling getObject().

Definition at line 755 of file SQLDBC.h.

Public Methods


Member Function Documentation

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::absolute int    row
 

Moves the cursor to the specified row number in this SQLDBC_ResultSet object.

If the row number is positive, the cursor moves to this specified row number with respect to the beginning of the result set. The first row is row number 1, the second is row number 2, and so on.

If the given row number is negative, the cursor moves to an 'absolute' position with respect to the end of the result set. For example, calling the method absolute(-1) positions the cursor on the last row; calling the method absolute(-2) moves the cursor to the next-to-last row, and so on.

An attempt to position the cursor beyond the first or last row in the result set leaves the cursor before the first row or after the last row.

Parameters:
row Row number where the cursor is moved to. A positive number specifies the absolute row number with respect to the beginning of the result set; a negative number specifies a absolute row number respect to the end of the result set.
Returns:
SQLDBC_OK if the cursor is on the result set; SQLDBC_NO_DATA_FOUND otherwise; SQLDBC_NOT_OK if a database access error occurs.

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::bindColumn const SQLDBC_UInt4    Index,
const SQLDBC_HostType    Type,
void *    paramAddr,
SQLDBC_Length   LengthIndicator,
const SQLDBC_Length    Size,
const SQLDBC_Bool    Terminate = SQLDBC_TRUE
 

Binds a user-supplied memory buffer to an SQL column of a result set.

Applications must use SQLDBC_ResultSetMetadata to retrieve information about the type and length of the columns of a result set.

Parameters:
Index [in] Parameter number. The parameter numbers in an SQL statement are, in increasing order, starting with 1.
Type [in] Parametertype of the output buffer
paramAddr [in] A pointer to a buffer for the parameter's data.
LengthIndicator [out] Pointer to a variable that stores the column length or the indicator value SQLDBC_NULL_DATA if the column contains the NULL value. For character data it contains on success the number of bytes copied to the buffer, except the number of bytes necessary for the zero-terminator, if the Terminate flag was set. If the source string exceeds the Size value SQLDBC_DATA_TRUNC will be returned and LengthIndicator is set to the number of bytes (except the terminator bytes) needed to copy without truncation.
Size [in] Length of the parameter buffer in bytes. The Size argument is only neccessary for non-integral datatypes. For character data the Size argument must be large enough to store the terminator byte(s) if the Terminate flag is set.
Terminate [in] Specifies that the output buffer must be finished with a C-style zero-terminator. The Terminate flag works only for the hostvar type character (ASCII, UCS2 or UTF8). As a default, all character data is zero-terminated.
Returns:
SQLDBC_OK on success SQLDBC_NOT_OK If a wrong argument value was passed. In this case an error is set on this SQLDBC_ResultSet object.
See also:
getObject
Todo:
: Indicator handling and truncation handling

void SQLDBC::SQLDBC_ConnectionItem::clearError   [inherited]
 

Deletes the error has been stored.

void SQLDBC::SQLDBC_ConnectionItem::clearWarnings   [inherited]
 

Deletes the warning stored in the SQLWarning object.

void SQLDBC::SQLDBC_ResultSet::close  
 

Closes this result set. Further operations are not allowed.

SQLDBC_ErrorHndl& SQLDBC::SQLDBC_ConnectionItem::error   [inherited]
 

Returns a reference to the ErrorHndl object.

Returns:
An SQLDBC_ErrorHndl object.

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::first  
 

Moves the cursor to the first row in this SQLDBC_ResultSet object.

Returns:
SQLDBC_OK if the cursor is on a valid row; SQLDBC_NO_DATA_FOUND if there are no rows in the result set; SQLDBC_NOT_OK if a database access error occurs or the result set type is FORWARD_ONLY

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::getObject const SQLDBC_Int4    Index,
const SQLDBC_HostType    Type,
void *    paramAddr,
SQLDBC_Length   LengthIndicator,
const SQLDBC_Length    Size,
const SQLDBC_Bool    Terminate = SQLDBC_TRUE
 

Retrieves and converts the value of the specified column of the current row to a buffer.

The current row in the result set object was set by the last positioning command or by the setPos() method of the SQLDBC_RowSet object.

Parameters:
Index Index of the column. The first column is column number 1, the second is column number 2, ...
Type Parameter type of the output buffer.
paramAddr A pointer to the parameters output buffer.
LengthIndicator [out] Pointer to a variable that stores the column length or the indicator value SQLDBC_NULL_DATA if the column contains the NULL value. For character data it contains on success the number of bytes copied to the buffer, except the number of bytes necessary for the zero-terminator, if the Terminate flag was set. If the source string exceeds the Size value SQLDBC_DATA_TRUNC will be returned and LengthIndicator is set to the number of bytes (except the terminator bytes) needed to copy without truncation.
Size [in] Length of the parameter buffer in bytes. The Size argument is only neccessary for non-integral datatypes. For character data the Size argument must be large enough to store the terminator byte(s) if the Terminate flag is set.
Terminate [in] Specifies that the output buffer must be finished with a C-style zero-terminator. The Terminate flag works only for the hostvar type character (ASCII, UCS2 or UTF8). As a default, all character data is zero-terminated.
Returns:
SQLDBC_OK on success SQLDBC_DATA_TRUNC if the output buffer was too small. SQLDBC_NOT_OK if a database access or conversion error occursed. In this case an error is set on this SQLDBC_ResultSet object.
See also:
bindColumn

const SQLDBC_UInt4 SQLDBC::SQLDBC_ResultSet::getResultCount   const
 

Returns number of rows of the current result set.

Returns:
Number of rows of the result set

SQLDBC_ResultSetMetaData* SQLDBC::SQLDBC_ResultSet::getResultSetMetaData  
 

Retrieves an SQLDBC_ResultSetMetaData object that contains information about the columns of this SQLDBC_ResultSet object.

Returns:
An SQLDBC_ResultSetMetaData object that describes the columns or NULL if the meta data cannot be retrieved.

const SQLDBC_UInt4 SQLDBC::SQLDBC_ResultSet::getRowNumber   const
 

Returns the current row number. The first row is row number 1, the second row number 2, and so on.

Returns:
The current row number or 0 if the cursor is positiooned outside the resultset.

SQLDBC_RowSet* SQLDBC::SQLDBC_ResultSet::getRowSet  
 

Retrieves the SQLDBC_RowSet returned by block cursor operations.

Returns:
A reference to an SQLDBC_RowSet object if the SQLDBC_ResultSet object has an SQLDBC_RowSet or NULL otherwise.

const SQLDBC_UInt4 SQLDBC::SQLDBC_ResultSet::getRowSetSize   const
 

Returns the size of the row array of bounded parameters.

Returns:
The size of the array of bound parameters
See also:
setRowSetSize

SQLDBC_Statement* SQLDBC::SQLDBC_ResultSet::getStatement  
 

Retrieves the SQLDBC_Statement object that belongs to the result set.

Returns:
A reference to the SQLDBC_Statement object that generate this result set.

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::last  
 

Moves the cursor to the last row in this SQLDBC_ResultSet object.

Returns:
SQLDBC_OK if the cursor is on a valid row; SQLDBC_NO_DATA_FOUND if there are no rows in the result set; SQLDBC_NOT_OK if a database access error occurs or the result set type is FORWARD_ONLY.

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::next  
 

Moves the cursor down one row from its current position.

A result set cursor is initially positioned before the first row; the first call of the member function next() positions the cursor to the first row set; the second call positions the cursor on the second row set, and so on.

An SQLDBC_ResultSet object's warning chain is cleared when the next call is done.

Returns:
SQLDBC_OK if the new current row is valid; SQLDBC_NO_DATA_FOUND if there are no more rows; SQLDBC_NOT_OK if a database access error occurs

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::previous  
 

Moves the cursor to the previous row in this SQLDBC_ResultSet object.

Returns:
SQLDBC_OK if the cursor is on a valid row; SQLDBC_NO_DATA_FOUND if it is outside the result set; SQLDBC_NOT_OK if a database access error occurs or the result set type is FORWARD_ONLY

SQLDBC_Retcode SQLDBC::SQLDBC_ResultSet::relative int    relativePos
 

Moves the cursor by a relative number of rows, either positive or negative.

Attempting to move the cursor beyond the first or last row in the result set positions the cursor before or after the first or last row. Calling relative(0) is valid, but does not change the cursor position.

Note:
Calling the method relative(1) is identical to calling the method next(). Calling the method relative(-1) is identical to calling the method previous().
Parameters:
relativePos An integer value specifying the number of rows by which the cursor is to be moved from its current position; a positive number moves the cursor forward; a negative number moves the cursor backward.
Returns:
SQLDBC_OK if the cursor is positioned on a row; SQLDBC_NO_DATA_FOUND otherwise; SQLDBC_NOT_OK if a database access error occurs or the result set type is FORWARD_ONLY.

void SQLDBC::SQLDBC_ResultSet::setFetchSize SQLDBC_Int2    fetchsize
 

Sets the desired fetch size. The fetch size setting is a hint to the runtime, and not a strict setting such as the row set size. If it is 1, the FETCH statements issued by the library will not be mass statements, making additional functionality, such as updating using the CURRENT OF predicate possible.

Parameters:
fetchsize The new fetch size.

void SQLDBC::SQLDBC_ResultSet::setRowSetSize SQLDBC_UInt4    rowsetsize
 

Sets the size of the row array of bounded parameters.

Parameters:
rowsetsize The number of rows.
See also:
getRowSetSize

SQLDBC_SQLWarning* SQLDBC::SQLDBC_ConnectionItem::warning   [inherited]
 

Returns a reference to an SQLWarning object stored in the SQLDBC_ConnectionItem object.

Returns:
The SQLWarning object stored in the item.


Friends And Related Function Documentation

friend class SQLDBC_Statement [friend]
 

Reimplemented from SQLDBC::SQLDBC_ConnectionItem.

Definition at line 1044 of file SQLDBC.h.

friend struct SQLDBC_StatementStorage [friend]
 

Definition at line 1045 of file SQLDBC.h.


The documentation for this class was generated from the following file: