 SourcePro® 2023.1 |
SourcePro® API Reference Guide |
Encapsulates an SQL DELETE statement.
More...
#include <rw/db/deleter.h>
Public Member Functions | |
| RWDBDeleter () | |
| RWDBDeleter (const RWDBDeleter &deleter) | |
| void | acquire (void) const |
| RWCString | asString () const |
| RWCString | asString (const RWDBConnection &conn) const |
| RWCString | asString (bool verbose) const |
| RWCString | asString (const RWDBConnection &conn, bool verbose) const |
| RWDBStatus | clear () |
| RWDBStatus::ErrorHandler | errorHandler () const |
| RWDBResult | execute () |
| RWDBResult | execute (const RWDBConnection &connection) |
| bool | isReady () const |
| bool | isValid () const |
| RWDBDeleter & | operator= (const RWDBDeleter &deleter) |
| void | release (void) const |
| void | setErrorHandler (RWDBStatus::ErrorHandler handler) |
| RWDBStatus | status () const |
| RWDBTable | table () const |
| RWDBDeleter & | where (const RWDBCriterion &criterion) |
| RWDBCriterion | where () const |
RWDBDeleter is an encapsulation of an SQL DELETE statement. The where() method of RWDBDeleter is used to specify a WHERE clause. The WHERE clause is encapsulated by an RWDBCriterion, which is some number of RWDBExpr instances combined with logical operators.
A DELETE statement does not normally produce results. However, the DB Interface Module recognizes that some database vendors provide triggers, which can cause results to be generated by a DELETE statement. Consequently, the execute() method of RWDBDeleter returns an RWDBResult, which is a sequence of zero or more RWDBTable objects. Applications are not obliged to request any tables from the returned object.
RWDBDeleter is designed around the Interface/Implementation paradigm. An RWDBDeleter instance is an interface to a reference-counted implementation; copy constructors and assignment operators produce additional references to a shared implementation. An RWDBDeleter implementation is a base class from which a family of database-specific deleter implementations is derived.
The encapsulated WHERE clause of an RWDBDeleter is an RWDBCriterion, which is composed of RWDBExpr instances. See RWDBCriterion, RWDBExpr, and RWDBColumn for details.
The result of execute() is an RWDBResult, which represents a sequence of zero or more RWDBTable instances. See RWDBResult and RWDBTable for details.
Example 1
For this example, we delete all the red hubcaps from the autoParts table:
Example 2
For this example, we delete all parts with a specific id by repeatedly using binding to a variable containing the id:
| RWDBDeleter::RWDBDeleter | ( | ) |
The default constructor creates an RWDBDeleter whose status is RWDBStatus::notInitialized. This constructor is provided as a convenience, for example, to declare an array of RWDBDeleter objects. A usable RWDBDeleter is obtained from an RWDBTable.
| RWDBDeleter::RWDBDeleter | ( | const RWDBDeleter & | deleter | ) |
Copy constructor. Self shares an implementation with deleter.
| void RWDBDeleter::acquire | ( | void | ) | const |
Attempts to acquire the internal mutex lock. If the mutex is already locked by another thread, the function blocks until the mutex is released. This function can be called from a const object.
|
inline |
Returns the SQL equivalent of:
This method returns an SQL statement that would be produced by executing self with an implicit RWDBConnection object. An implicit RWDBConnection object inherits the time zone setting from the producer RWDBDatabase instance. Hence, the time zone setting of the producer RWDBDatabase object will be used for creating the string representations of any RWDateTime instances in self.
The behavior of this method depends upon the RWDBDatabase::verboseAsString() setting in the producer RWDBDatabase instance.
false, the SQL returned is the same as that passed to the database for execution. This is the default.true, any placeholders in the returned SQL are replaced with their bound values.true, the SQL returned by this method may not be a valid SQL statement. However, this method's return value is not necessarily the same SQL that is sent to the database for execution. For example, if an RWDBBlob object is bound, calling this method with RWDBDatabase::verboseAsString() set to true will result in a string with blob data returned as hex numbers, such as 0x0A32F5.
|
inline |
Returns the SQL equivalent of:
This method returns an SQL statement that would be produced by executing self with conn. The time zone setting of conn will be used for creating string representations of any RWDateTime instances in self.
The behavior of this asString() method depends upon the RWDBDatabase::verboseAsString() setting in the producer RWDBDatabase instance.
false,the SQL returned is the same as that passed to the database for execution. This is the default.true, any placeholders in the returned SQL are replaced with their bound values.true, the SQL returned by this method may not be a valid SQL statement. However, this method's return value is not necessarily the same SQL that is sent to the database for execution. For example, if an RWDBBlob object is bound, calling this method with RWDBDatabase::verboseAsString() set to true will result in a string with blob data returned as hex numbers, such as 0x0A32F5.
|
inline |
Returns the SQL equivalent of:
This method returns an SQL statement that would be produced by executing self with an implicit RWDBConnection object. An implicit RWDBConnection object inherits the time zone setting from the producer RWDBDatabase instance. Hence, the time zone setting of the producer RWDBDatabase object will be used for creating the string representations of any RWDateTime instances in self.
The behavior of this method depends on the value of verbose, and is independent of the RWDBDatabase::verboseAsString() setting.
false, the SQL returned is the same as that passed to the database for execution.true, any placeholders in the returned SQL are replaced with their bound values although the SQL passed to the database for execution will not be affected.true may not be a valid SQL statement. However, this is not necessarily the same SQL that is sent to the database for execution. For example, if an RWDBBlob object is bound, calling this method with verbose as true will result in a string with blob data returned as hex numbers, such as 0x0A32F5.
|
inline |
Returns the SQL equivalent of:
This method returns an SQL statement that would be produced by executing self with conn. The time zone setting of conn will be used for creating string representations of any RWDateTime instances in self.
The behavior of this method depends on the value of verbose, and is independent of the RWDBDatabase::verboseAsString() setting.
false, the SQL returned is the same as that passed to the database for execution.true, any placeholders in the returned SQL are replaced with their bound values although the SQL passed to the database for execution will not be affected.true may not be a valid SQL statement. However, this is not necessarily the same SQL that is sent to the database for execution. For example, if an RWDBBlob object is bound, calling this method with verbose as true will result in a string with blob data returned as hex numbers, such as 0x0A32F5.| RWDBStatus RWDBDeleter::clear | ( | ) |
Clears self's WHERE clause and internal controls.
| RWDBStatus::ErrorHandler RWDBDeleter::errorHandler | ( | ) | const |
Returns the error handler attached to self.
| RWDBResult RWDBDeleter::execute | ( | ) |
Uses a default database connection to cause the SQL statement encapsulated by self to be executed.
| RWDBResult RWDBDeleter::execute | ( | const RWDBConnection & | connection | ) |
Uses the supplied connection to cause the SQL statement encapsulated by self to be executed. This function can behave asynchronously if executed using an asynchronous connection.
| bool RWDBDeleter::isReady | ( | ) | const |
Returns true if the object is in ready state, indicating that accessing the object will not block. Accessing a nonready object may potentially block.
| bool RWDBDeleter::isValid | ( | ) | const |
Returns true if self's status is RWDBStatus::ok, otherwise returns false. Does not return false if the previously executed statement failed. You must check the status of the RWDBResult returned from execute() instead of the status of the RWDBDeleter object.
| RWDBDeleter& RWDBDeleter::operator= | ( | const RWDBDeleter & | deleter | ) |
Assignment operator. Self shares an implementation with deleter.
| void RWDBDeleter::release | ( | void | ) | const |
Releases a previously acquired mutex. This function can be called from a const object.
| void RWDBDeleter::setErrorHandler | ( | RWDBStatus::ErrorHandler | handler | ) |
Installs handler as self's error handler. The supplied handler is inherited by all objects produced by self. By default, the RWDBStatus::ErrorHandler is inherited from the object that produced self; this method overrides the default.
| RWDBStatus RWDBDeleter::status | ( | ) | const |
Returns the current status of self.
| RWDBTable RWDBDeleter::table | ( | ) | const |
Returns the RWDBTable that produced self. Returns an RWDBTable whose status is RWDBStatus::notInitialized if self was produced with the default constructor.
| RWDBDeleter& RWDBDeleter::where | ( | const RWDBCriterion & | criterion | ) |
Specifies criterion as self's SQL WHERE clause. If self already has a WHERE clause, this method replaces it. Specifying an empty criterion clears self's WHERE clause. Notice that a deleter without a WHERE clause deletes all rows from its table. Returns a reference to self.
| RWDBCriterion RWDBDeleter::where | ( | ) | const |
Returns a copy of self's RWDBCriterion, an encapsulated SQL WHERE clause. Returns an empty RWDBCriterion if self has no WHERE clause.
|
Copyright © 2023 Rogue Wave Software, Inc., a Perforce company. All Rights Reserved. |