Basics: demonstrates basic use of the Symbian OS DBMS

These files are found in: examples\SysLibs\Dbms\Basics

The files reproduced here are the main files contained in the examples directory. Some extra files may be needed to run the examples, and these will be found in the appropriate examples directory.

 DBMS Interface to Databases - Basic Creation and Use
//
// Copyright (c) 2000 Symbian Ltd.  All rights reserved.


// Example to demonstrate basic database creation and use


#include "CommonToDBMSEx.h"
    
                // Create a database and its structure
LOCAL_C void doMakeDatabaseL(const TDesC& aDatabaseFileName);

                // Add some records to the database
LOCAL_C void doAddDataL(const TDesC& aDatabaseFileName);

                // Display the rows
LOCAL_C void doShowL(const TDesC& aHeading,RDbRowSet& aSet);

                // Create the CDs table
LOCAL_C void doCreateTableL(RDbDatabase& aDatabase);

                // Create the CDs index
LOCAL_C void doCreateIndexL(RDbDatabase& aDatabase);


//  Do the example
LOCAL_C void doExampleL()
    {
    _LIT(KDbCreateDb,"dbcreate.db");

                // The database dbcreate.db is created as a permanent file store 
                // in the app's private directory
    User::LeaveIfError(fsSession.CreatePrivatePath(EDriveC));
    TFileName name;
    User::LeaveIfError(fsSession.PrivatePath(name));
    name.Append(KDbCreateDb);
                // create database
    doMakeDatabaseL(name);
                // add items
    doAddDataL(name);
    }


LOCAL_C void doMakeDatabaseL(const TDesC& aDatabaseFileName)
    {
                // construct a file store object - the file to contain the
                // database replaces any existing file of the same name.
    CFileStore* store = CPermanentFileStore::ReplaceLC(fsSession,aDatabaseFileName,EFileRead|EFileWrite);
                // Complete file store creation
    store->SetTypeL(store->Layout());

                // Create a database in the store
    RDbStoreDatabase database;
    TStreamId id=database.CreateL(store);
                // NB. The database won't be closed on failure
                //     Cleanup can be done; more usually database objects
                //     are not automatic variables.

                // Keep database id as root of store
    store->SetRootL(id);

                // Complete database creation by commiting the store
    store->CommitL();

                // create the CDs table
    doCreateTableL(database);

                // create an index
    doCreateIndexL(database);

                // close the database
    database.Close();

                // Do not commit store: database has taken control of commit
    CleanupStack::PopAndDestroy();
    }


LOCAL_C void doAddDataL(const TDesC& aDatabaseFileName)
    {
    _LIT(KSQLStatement,"select title,artist,price from CDs order by artist,title");
    _LIT(KComposition1, "Enigma Variations");
    _LIT(KComposer1, "Elgar");
    _LIT(KComposition2, "Symphony no. 5");
    _LIT(KComposer2, "Beethoven");

                // Open the file store
    CFileStore* store = CFileStore::OpenLC(fsSession,aDatabaseFileName,EFileRead|EFileWrite);

                // open the database from the root stream
    RDbStoreDatabase database;
    database.OpenL(store,store->Root());

                // create a view on the database
    RDbView view;
    User::LeaveIfError(view.Prepare(database,TDbQuery(KSQLStatement,EDbCompareNormal)));
    User::LeaveIfError(view.EvaluateAll());
                // NB. a similar caveat about cleanup applies as mentioned above

                // insert a row
    view.InsertL();
                // column numbers match the order specified in the select statement
                // data type must match almost exactly (a few exceptions)
    
    view.SetColL(1,KComposition1);
    view.SetColL(2,KComposer1);
    view.SetColL(3,1299);
                // complete the insertion
    view.PutL();

                // insert another row
    view.InsertL();


    view.SetColL(1,KComposition2);
    view.SetColL(2,KComposer2);
    view.SetColL(3,1499);
                // complete the insertion
    view.PutL();

                // show the records
    _LIT(KShowInfo, "Rowset contents...");
    doShowL(KShowInfo, view);

                // close the view
    view.Close();
                
                // close the database
    database.Close();

                // Do not commit store: database has taken control of commit
    CleanupStack::PopAndDestroy();
    }


LOCAL_C void doShowL(const TDesC& aHeading,RDbRowSet& aSet)
    {
    _LIT(KNewline, "\n") ;
    _LIT(KRowHeadingFormatter, "\n%d row(s):");
    _LIT(KRowFormatter, "\n  %S, %S:  %d.%02.2d");

    console->Printf(KNewline);
    console->Printf(aHeading);

    console->Printf(KRowHeadingFormatter,aSet.CountL());
                // iterate across the row set
    for (aSet.FirstL();aSet.AtRow();aSet.NextL())
        {
                // retrieve the row
        aSet.GetL();
                // while the rowset is on this row, can use a TPtrC to
                // refer to any text columns
        TPtrC title=aSet.ColDes(1);
        TPtrC artist=aSet.ColDes(2);

                // simple currency formatting; not locale-dependent
        TInt pricePounds=(aSet.ColInt(3)/100);
        TInt pricePence=(aSet.ColInt(3)-(pricePounds*100));
        console->Printf(KRowFormatter,&artist,&title,pricePounds,pricePence);
        }
    console->Printf(KNewline);
    }


LOCAL_C void doCreateTableL(RDbDatabase& aDatabase)
    {
    _LIT(KCol1, "Artist");
    _LIT(KCol2, "Title");
    _LIT(KCol3, "Price");
    _LIT(KTable, "CDs");

                // Create a table definition
    CDbColSet* columns=CDbColSet::NewLC();

                // add the columns
                // text columns default to 50 characters (variable length)
    columns->AddL(TDbCol(KCol1,EDbColText));

                // specify an alternative length
    TDbCol title(KCol2,EDbColText,60);
    title.iAttributes=TDbCol::ENotNull;
    columns->AddL(title);

    TDbCol price(KCol3,EDbColInt32);

                // columns are Nullable by default
    price.iAttributes=TDbCol::ENotNull;
    columns->AddL(price);

                // Create a table
    User::LeaveIfError(aDatabase.CreateTable(KTable,*columns));
                
        // cleanup the column set
    CleanupStack::PopAndDestroy();
    }


LOCAL_C void doCreateIndexL(RDbDatabase& aDatabase)
    {
    _LIT(KCol1, "Artist");
    _LIT(KCol2, "Title");
    _LIT(KTable, "CDs");

                // create the index key
    CDbKey* key=CDbKey::NewLC();

                // add the key columns
    TDbKeyCol artist(KCol1);
    key->AddL(artist);
    TDbKeyCol title(KCol2);
    key->AddL(title);

                // create the index
    User::LeaveIfError(aDatabase.CreateIndex(KTable,KTable,*key));

                // cleanup the key
    CleanupStack::PopAndDestroy();
    }

// Basics.mmp
//
// Copyright (c) 2000 Symbian Ltd.  All rights reserved.

// using relative paths for source and userinclude directories

TARGET        DBMSBasics.exe
TARGETTYPE    exe
UID           0 0x1020e43b
VENDORID 0x70000001

SOURCEPATH    .
SOURCE        Basics.cpp

USERINCLUDE   .
USERINCLUDE   ..\..\CommonFramework
SYSTEMINCLUDE \Epoc32\include

LIBRARY       euser.lib efsrv.lib edbms.lib estor.lib

// BLD.INF
// Component description file
//
// Copyright (c) 2000 Symbian Ltd.  All rights reserved.

PRJ_MMPFILES

Basics.mmp

This is an example of database manipulation using the DBMS.

Initially the database is created as a permanent file store, using CFileStore routines. A table ("CDs") is created with three fields ("Artist", "Title" and "Price") and this is then indexed on the "Artist" and "Title" fields.

To prove the correct action of the previous code, the example iterates through the database, printing the contents to the console. Finally, the database is closed and the example exits.

The example should be run from the command line with no parameters.

• RDbView

• RDbStoreDatabase

• TDbCol

• TDbKeyCol

• CDbColSet

• RDbRowSet

• CDbKey

• TParse

• TStreamId

• CFileStore