Categories: Symbian C++ | Code Examples | Files/Data | S60 3rd Edition, Feature Pack 2

This page was last modified 07:40, 2 May 2008.

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Overview

The RSqlStatement class provides functionality to execute all types of SQL statements when using the SQL API. RSqlStatement encapsulates an SQL statement and the data that it returns. RSqlStatement statements can be executed with the methods Exec() and Next(). The method Exec() is used when the statement does not return any data and Next() when the statement returns data. This snippet gives some examples on how to use the Exec() method.

Statements use so-called placeholders (:) in descriptors to mark positions where dynamic data is inserted at runtime. The user can bind the actual data to placeholders with different Bind() methods, such as BindText(). It is good practise to resolve the placeholder index with the RSqlStatement::ParameterIndex() method, and not to use hardcoded values.

NOTE: SQL statements can also be executed using the RSqlDatabase::Exec() methods, but the behaviour is more limited because the RSqlDatabase::Exec() method is not able to return any records.

If asyncronous functionality is required, RSqlDatabase and RSqlStatement classes have also asyncronous versions of Exec() methods.

This snippet can be self-signed.

MMP file

The following libraries are required:

LIBRARY  euser.lib
LIBRARY  sqldb.lib

The following capabilities are needed to test the example secure database:

CAPABILITY ReadUserData
CAPABILITY WriteUserData

Preconditions

Databases nonsecure.db and [UID3]secure.db need to be created before executing this code snippet. See CS000925 - Using SQL API for creating non-secure and secure databases.

Source file

#include <e32base.h>
#include <SqlDb.h>
 
void ExecStatementsL()
  {
  RSqlDatabase database;
 
  _LIT(KSecureDbName, "[E80000AF]secure.db");
 
//== Insert into table statement==
  TInt error = database.Open(KSecureDbName);
 
  if (error == KErrNone)
    {
    CleanupClosePushL(database);
 
    RSqlStatement sqlInsertIntoBooksStatement;
 
    _LIT(KSqlInsertIntoBooksTable, "INSERT INTO BOOKS(ID, TITLE, AUTHOR) 
VALUES(:Val1, :Val2, :Val3)");
    TInt ret = sqlInsertIntoBooksStatement.Prepare(database, KSqlInsertIntoBooksTable);
 
    if(ret == KErrNone)
      {
      CleanupClosePushL(sqlInsertIntoBooksStatement);
 
      TInt paramIndex1 = sqlInsertIntoBooksStatement.ParameterIndex(_L(":Val1"));
      TInt paramIndex2 = sqlInsertIntoBooksStatement.ParameterIndex(_L(":Val2"));
      TInt paramIndex3 = sqlInsertIntoBooksStatement.ParameterIndex(_L(":Val3"));
 
      User::LeaveIfError(sqlInsertIntoBooksStatement.BindInt(paramIndex1, 10));
      User::LeaveIfError(sqlInsertIntoBooksStatement.BindText(paramIndex2, 
_L("RSqlStatementTitle")));
      User::LeaveIfError(sqlInsertIntoBooksStatement.BindText(paramIndex3, 
_L("RSqlStatementAuthor")));
 
      User::LeaveIfError(sqlInsertIntoBooksStatement.Exec());
 
      //It is possible to reuse statement after reset call
      User::LeaveIfError(sqlInsertIntoBooksStatement.Reset());
      //Bind new values here...
 
      CleanupStack::PopAndDestroy(1); //KSqlInsertIntoBooksStatement
 
      }
    else
      {
      //prepare sql statement failed
      }
    CleanupStack::PopAndDestroy(1); //database
    }
  else
    {
    //open database failed
    }
 
//== Update statement==
 
  _LIT(KNonSecureDbName, "\\nonsecure.db");
 
  error = database.Open(KNonSecureDbName);
 
  if (error == KErrNone)
    {
    CleanupClosePushL(database);
 
    RSqlStatement sqlUpdateMoviesRowStatement;
 
    _LIT(KSqlUpdateMoviesRow, "UPDATE MOVIES SET TITLE=:Val1 WHERE ID=:Val2");
    TInt ret = sqlUpdateMoviesRowStatement.Prepare(database, KSqlUpdateMoviesRow);
 
    if(ret == KErrNone)
      {
      CleanupClosePushL(sqlUpdateMoviesRowStatement);
 
      TInt paramIndex1 = sqlUpdateMoviesRowStatement.ParameterIndex(_L(":Val1"));
      TInt paramIndex2 = sqlUpdateMoviesRowStatement.ParameterIndex(_L(":Val2"));
 
      User::LeaveIfError(sqlUpdateMoviesRowStatement.BindText(paramIndex1, 
_L("RSqlStatementUpdatedTitle")));
      User::LeaveIfError(sqlUpdateMoviesRowStatement.BindInt(paramIndex2, 1));
 
      User::LeaveIfError(sqlUpdateMoviesRowStatement.Exec());
 
      //It is possible to reuse statement after reset call
      User::LeaveIfError(sqlUpdateMoviesRowStatement.Reset());
      //Bind new values here...
 
      CleanupStack::PopAndDestroy(1); //sqlUpdateMoviesRowStatement
 
      }
    else
      {
      //prepare sql statement failed
      }
    CleanupStack::PopAndDestroy(1); //database
    }
  else
    {
    //open database failed
    }
 
//== Delete statement==
 
  /* Note: It is possible to use a RSqlStatement object to delete rows from table,
   * but it is computationally more expensive and it is not recommended.
   * Use RSqlDatabase::Exec() method instead */
 
  error = database.Open(KSecureDbName);
 
  if (error == KErrNone)
    {
    _LIT(KSqlDeleteFromBooksTable, "DELETE FROM BOOKS WHERE ID > 9;");
    TInt ret = database.Exec(KSqlDeleteFromBooksTable);
 
    database.Close();
    }
  else
    {
    //open database failed
    }
 
  }

Postconditions

The RSqlStatement class is used to insert a new row into the table ([UID3]secure.db) and to update the existing row (nonsecure.db). The RSqlDatabase is used to delete one row from the table ([UID3]secure.db).

See also

• CS000925 - Using SQL API for creating non-secure and secure databases
• CS000926 - Using SQL API for attaching and detaching databases
• CS000928 - Using SQL API with SQL statements which return data
• CS000929 - Using SQL API with scalar queries
• CS000930 - Using SQL API with data streams