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DBMS Rowsets »
RDbView
Location:
d32dbms.h
Link against: edbms.lib
RDbView
Support
Supported from 5.0
Description
Generates rowsets from an SQL query. The query is prepared and
evaluated using the interface to this class, while the rowset is manipulated
using the RDbRowset base class.
There are no special rules to consider when deriving from this
class.
Derivation
RDbRowSet | An abstract base class that provides functionality which is shared between SQL view objects and Table objects |
RDbView | Generates rowsets from an SQL query |
|
Defined in RDbView:
Evaluate(), EvaluateAll(), Prepare(), Unevaluated()
Inherited from RDbRowSet:
AtBeginning(),
AtEnd(),
AtRow(),
BeginningL(),
Bookmark(),
Cancel(),
Close(),
ColCount(),
ColDef(),
ColDes(),
ColDes16(),
ColDes8(),
ColInt(),
ColInt16(),
ColInt32(),
ColInt64(),
ColInt8(),
ColLength(),
ColReal(),
ColReal32(),
ColReal64(),
ColSetL(),
ColSize(),
ColTime(),
ColType(),
ColUint(),
ColUint16(),
ColUint32(),
ColUint8(),
CountL(),
DeleteL(),
EBackwards,
EBeginning,
EEnd,
EEnsure,
EFirst,
EForwards,
EInsertOnly,
ELast,
ENext,
EPrevious,
EQuick,
EReadOnly,
EUpdatable,
EndL(),
FindL(),
FirstL(),
GetL(),
GotoL(),
InsertCopyL(),
InsertL(),
IsColNull(),
IsEmptyL(),
LastL(),
MatchL(),
NextL(),
PreviousL(),
PutL(),
Reset(),
SetColL(),
SetColNullL(),
TAccess,
TAccuracy,
TDirection,
TPosition,
UpdateL()
Preparation
TInt Prepare(RDbDatabase& aDatabase,const TDbQuery& aQuery,TAccess anAccess=EUpdatable);
Description
Prepares the view object for evaluating an SQL
select-statement.
Following preparation, the rowset object can always provide
schema information, but the view may first require evaluation to generate the
rowset for navigation.
Parameters
RDbDatabase& aDatabase |
The database on which to execute the query. |
const TDbQuery& aQuery |
The SQL query and the text comparison mode for the
constraint. |
TAccess anAccess=EUpdatable |
The access specification for the rowset. By default, updatable
access is given. |
|
Return value
TInt |
KErrNone, if successful, otherwise one of the
other system-wide error codes. Specifically: KErrNotFound if The
table does not exist in the database or a column name in the SQL query does not
exist.KErrNotSupported if a sort-specification in the SQL query
cannot be provided by an index.KErrArgument if an invalid or
unrecognised SQL syntax was used.KErrGeneral if there is a column
type mismatch in a predicate in the SQL query or if a date-literal in the SQL
query was invalid.KErrOverflow if a number-literal in the SQL
query for an integral column was too large (did not fit in a 32-bit integral
representation). This can also be one of the DBMS database error codes..
|
|
See also:
TInt Prepare(RDbDatabase& aDatabase,const TDbQuery& aQuery,const TDbWindow& aWindow);
Description
Prepares the view object for evaluating an SQL select-statement
and specifies the evaluation window shape for the rowset.
The function does not specify the access specification for the
rowset — updatable access is given.
Following preparation, the rowset object can always provide
schema information, but the view may first require evaluation to generate the
rowset for navigation.
Parameters
RDbDatabase& aDatabase |
The database on which to execute the query. |
const TDbQuery& aQuery |
The SQL query and the text comparison mode for the
constraint. |
const TDbWindow& aWindow |
The desired evaluation window shape for the rowset. If this
parameter is omitted, an alternative overload is called — e.g. no
pre-evaluation window is requested. |
|
Return value
TInt |
KErrNone, if successful, otherwise one of the other
system-wide error codes. Specifically: KErrNotFound if The table
does not exist in the database or a column name in the SQL query does not
exist.KErrNotSupported if a sort-specification in the SQL query
cannot be provided by an index.KErrArgument if an invalid or
unrecognised SQL syntax was used.KErrGeneral if there is a column
type mismatch in a predicate in the SQL query or if a date-literal in the SQL
query was invalid.KErrOverflow if a number-literal in the SQL
query for an integral column was too large (did not fit in a 32-bit integral
representation). This can also be one of the DBMS database error codes.
|
|
See also:
TInt Prepare(RDbDatabase& aDatabase,const TDbQuery& aQuery,const TDbWindow& aWindow,TAccess anAccess);
Description
Prepares the view object for evaluating an SQL select-statement,
specifies the evaluation window shape for the rowset, and sets the access
specification for the rowset.
Following preparation, the rowset object can always provide schema
information, but the view may first require evaluation to generate the rowset
for navigation.
Parameters
RDbDatabase& aDatabase |
The database on which to execute the query. |
const TDbQuery& aQuery |
The SQL query and the text comparison mode for the
constraint. |
const TDbWindow& aWindow |
The desired evaluation window shape for the rowset. If this
parameter is omitted, an alternative overload is called — e.g. no
pre-evaluation window is requested. |
TAccess anAccess |
The access specification for the rowset. If omitted, updatable
access is given. |
|
Return value
TInt |
KErrNone, if successful, otherwise one of the other
system-wide error codes. Specifically:KErrNotFound if The table
does not exist in the database or a column name in the SQL query does not
exist.KErrNotSupported if a sort-specification in the SQL query
cannot be provided by an index.KErrArgument if an invalid or
unrecognised SQL syntax was used.KErrGeneral if there is a column
type mismatch in a predicate in the SQL query or if a date-literal in the SQL
query was invalid.KErrOverflow if a number-literal in the SQL
query for an integral column was too large (did not fit in a 32-bit integral
representation). This can also be one of the DBMS database error codes.
|
|
See also:
TInt Evaluate();
Description
Performs a single step of the view evaluation, and returns when the
step is complete. To completely evaluate a view in one go,
EvaluateAll() should be used.
Return value
TInt |
0, evaluation is complete.>
0, more
evaluation can be done. < 0, an error code, see the class overview for more
information. |
|
void Evaluate(TRequestStatus& aStatus);
Description
Performs a single step of the view evaluation, returning immediately
and signalling when the step is complete.
This function is most effectively used when the view evaluation is
carried out from an active object.
Parameters
TRequestStatus& aStatus |
The request status used to contain completion information for the
function. On completion, the status value should be interpreted as follows: 0,
evaluation is complete.>
0, more evaluation can be
done. < 0, an error code, see the class overview for more
information. |
|
TInt EvaluateAll();
Description
Use this function to fully evaluate the view. It is equivalent to:
while (Unevaluated()) { Evaluate(); }
Return value
TInt |
KErrNone, if successful, otherwise one of the system wide
error codes.
|
|
See also:
TBool Unevaluated() const;
Description
Tests whether any more evaluation can be done to a
view.
Return value
TBool |
True, if the view can be further evaluated; false, if evaluation will
have no effect. |
|
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