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Represents foreign keys in a database, used when creating a database table or fetching a database table schema. More...
#include <rw/db/forkey.h>
RWDBForeignKey is used to represent foreign keys in a database, used when building up an RWDBSchema in preparation for an RWDBDatabase::createTable() call. An RWDBForeignKey is also used as elements of lists that are returned from RWDBTable::foreignKeys() and RWDBTable::referredToBy(). RWDBForeignKey has much the same interface and semantics as RWDBSchema.
RWDBForeignKey is designed around the Interface/Implementation paradigm. An RWDBForeignKey instance is an interface to a reference-counted implementation; copy constructors and assignment operators produce additional references to a shared implementation. An RWDBForeignKey implementation is a base class from which a family of database-specific foreign key implementations is derived.
#include <rw/db/forkey.h> RWDBForeignKey fk;
See also: RWDBDatabase, RWDBTable, RWDBForeignKeyList, and RWDBSchema.
Example 1
In this example, two tables are created, a Professor table with pid as the primary key and a Course table with profid as a foreign key into the Professor table.
RWDBSchema profSchema; RWDBSchema primeKey; RWDBColumn aCol1; aCol1.name("profname").type(RWDBValue::String). nullAllowed(false).storageLength(30); profSchema.appendColumn( aCol1 ); RWDBColumn aCol2; aCol2.name("pid").type(RWDBValue::Int).nullAllowed(false); profSchema.appendColumn( aCol2 ); primeKey.appendColumn( profSchema["pid"] ); //pid is the //primary key; profSchema.primaryKey( primeKey ); //Attach the //primary key //to the //professor schema. // Create the Professor table aDatabase.createTable("Professor", profSchema); // Now create the Course table RWDBSchema courseSchema; courseSchema.appendColumn( aCol1 ); courseSchema.appendColumn( aCol2 ); RWDBColumn aCol3; aCol3.name("coursename").type(RWDBValue::String). nullAllowed(false).storageLength(30); courseSchema.appendColumn( aCol3 ); RWDBColumn aCol4; aCol4.name("profid").type(RWDBValue::Int).nullAllowed(false); courseSchema.appendColumn( aCol4 ); RWDBForeignKey keyToProf("Professor"); keyToProf.appendColumn(courseSchema["profid"]); //profid is the //foreign key for the //Professor table. courseSchema.foreignKey( keyToProf ); //Attach the foreign //key to the //course Schema. aDatabase.createTable("Course", courseSchema); //Create the Course //table.
Example 2
This next example queries the Course table for its foreign key into the Professor table. It assumes the tables have been set up according to the example above.
RWDBTable course = aDatabase.table("Course"); assert( course.exists() ); RWDBForeignKeyList aList; RWDBStatus status = course.foreignKeys("Professor", aList); RWDBForeignKey& fKey = aList[0]; assert( fKey.referenceName() == "Professor" ); assert( fKey[0].name() == "profid");
| RWDBForeignKey::RWDBForeignKey | ( | ) |
Creates an empty RWDBForeignKey. Provided for convenience only.
| RWDBForeignKey::RWDBForeignKey | ( | const RWCString & | refName, | |
| Constraint | updateConstraint = Restrict, |
|||
| Constraint | deleteConstraint = Restrict | |||
| ) |
This constructor creates an empty RWDBForeignKey, that is, one with zero columns. The name of the table to which self refers is refName. The update constraint associated with self is updateConstraint. The delete constraint associated with self is deleteConstraint.
| RWDBForeignKey::RWDBForeignKey | ( | const RWCString & | constraintName, | |
| const RWCString & | refName, | |||
| Constraint | updateConstraint = Restrict, |
|||
| Constraint | deleteConstraint = Restrict | |||
| ) |
Constructor.
| RWDBForeignKey::RWDBForeignKey | ( | const RWDBForeignKey & | fk | ) |
Copy constructor. Self shares an implementation with fk.
| RWDBColumn RWDBForeignKey::appendColumn | ( | const RWDBColumn & | col | ) |
Creates a copy of col and appends to self. Returns the copy col.
| RWCString RWDBForeignKey::asString | ( | const RWDBPhraseBook & | phraseBook | ) | const |
Returns an RWCString representing self as string based on the format found in phraseBook.
| RWDBColumn RWDBForeignKey::column | ( | const RWCString & | name, | |
| RWCString::caseCompare | caseCompare | |||
| ) | const |
Returns a shallow copy of the column from self whose name matches the given name, according to caseCompare. If there is no match, returns an RWDBColumn whose status is RWDBStatus::columnNotFound.
| RWDBColumn RWDBForeignKey::column | ( | const RWCString & | name | ) | const |
Returns a shallow copy of the column from self whose name matches the given name. If there is no match, returns an RWDBColumn whose status is RWDBStatus::columnNotFound.
| RWDBColumn RWDBForeignKey::column | ( | size_t | index | ) | const |
Returns a deep copy of the column from self at the specified index. If the index is out of range, returns an RWDBColumn whose status is RWDBStatus::invalidPosition.
| void RWDBForeignKey::constraintName | ( | const RWCString & | newName | ) |
Sets the constraint name of self to be newName. Note that this does not change the name of the foreign key in a table which already exists in the database.
| RWCString RWDBForeignKey::constraintName | ( | ) | const |
Returns the constraint name of this foreign key.
| void RWDBForeignKey::deleteConstraint | ( | Constraint | newConstraint | ) |
Sets the delete constraint of self to the newConstraint. Note that this does not change the delete constraint of a foreign key of a table which already exists.
| Constraint RWDBForeignKey::deleteConstraint | ( | ) | const |
Returns the delete constraint of self.
| size_t RWDBForeignKey::entries | ( | ) | const |
Returns the number of RWDBColumn instances in self.
| RWDBStatus::ErrorHandler RWDBForeignKey::errorHandler | ( | ) | const |
Returns the error handler attached to self.
| size_t RWDBForeignKey::index | ( | const RWDBColumn & | column | ) | const |
Returns the index of the first RWDBColumn in self with the same name as the name of the given column. Returns RW_NPOS if no such column is found.
| size_t RWDBForeignKey::index | ( | const RWCString & | name, | |
| RWCString::caseCompare | caseCompare | |||
| ) | const |
Returns the index of the first column from self whose name matches the given name, according to caseCompare. If there is no match, returns RW_NPOS.
| size_t RWDBForeignKey::index | ( | const RWCString & | name | ) | const |
Returns the index of the first RWDBColumn in self with the given name. Returns RW_NPOS if no such column is found.
| bool RWDBForeignKey::isEmpty | ( | ) | const |
Returns true if self contains zero entries, otherwise returns false.
| bool RWDBForeignKey::isValid | ( | ) | const |
Returns true if self's status is RWDBStatus::ok, otherwise returns false.
| RWDBForeignKey& RWDBForeignKey::operator= | ( | const RWDBForeignKey & | fk | ) |
Assignment operator. Self shares an implementation with fk.
| RWDBColumn RWDBForeignKey::operator[] | ( | const RWCString & | name | ) | const |
Returns the first RWDBColumn in self with the given name. If no such column exists, returns an RWDBColumn with a status of RWDBStatus::columnNotFound. Note that the returned RWDBColumn is not a deep copy; modifications to RWDBColumn change the containing schema.
| RWDBColumn RWDBForeignKey::operator[] | ( | size_t | index | ) | const |
Returns the RWDBColumn in self at position index. If the index is out of range, returns an RWDBColumn with a status of RWDBStatus::invalidPosition. Indexing into an empty RWDBForeignKey is treated as out of range. Note that the returned RWDBColumn is not a deep copy; modifications to RWDBColumn change the containing RWDBForeignKey.
| void RWDBForeignKey::referenceKey | ( | const RWDBSchema & | schema | ) |
Sets the referenced key of self to schema. This does not change the referenced key of a foreign key in a table that already exists in the database.
| RWDBSchema& RWDBForeignKey::referenceKey | ( | ) |
Returns a reference to the currently held reference key of self.
| RWCString RWDBForeignKey::referenceName | ( | ) | const |
Returns the reference name of self.
| void RWDBForeignKey::setErrorHandler | ( | RWDBStatus::ErrorHandler | handler | ) |
Installs handler as self's error handler. The supplied handler is inherited by all objects produced by self. By default, an RWDBStatus::ErrorHandler is inherited from the object that produced self; this method overrides the default.
| RWDBStatus RWDBForeignKey::status | ( | ) | const |
Returns the current status of self.
| void RWDBForeignKey::updateConstraint | ( | Constraint | newConstraint | ) |
Sets the update constraint of self to the newConstraint. Note that this does not change the update constraint of a foreign key of a table that already exists.
| Constraint RWDBForeignKey::updateConstraint | ( | ) | const |
Returns the update constraint of self.
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