diff -r 4816d766a08a -r f345bda72bc4 Symbian3/PDK/Source/GUID-C60DAE3D-7FB9-5619-9E5D-476A430705AF.dita --- a/Symbian3/PDK/Source/GUID-C60DAE3D-7FB9-5619-9E5D-476A430705AF.dita Tue Mar 30 11:42:04 2010 +0100 +++ b/Symbian3/PDK/Source/GUID-C60DAE3D-7FB9-5619-9E5D-476A430705AF.dita Tue Mar 30 11:56:28 2010 +0100 @@ -1,33 +1,104 @@ - - - - - -Querying a databaseThis tutorial shows you how to create a simple SQL database query.
Introduction

This tutorial shows you how to wrap a SQL query statement into an RSqlStatement object to query a database.

The SQL statement used for the tutorial is shown here:

SELECT name FROM countries WHERE population > 10

The (SELECT) results of the query will be the value in the 'name' column FROM the 'countries' table WHERE the value of the 'population' column of the same record is > the value specified.

Procedure

  1. Prepare the Statement:

    The steps to prepare a SQL statement are shown here.

    1. Set up some constants used by the SQL statement object to define the SQL query:

      _LIT(kName,"name"); -_LIT(kPopulation,"population"); -_LIT(kVal,":Value"); -_LIT(kQueryString,"SELECT name FROM countries WHERE population > :Value");

      This defines the query parameters.

    2. Instantiate the RSqlStatement SQL statement:

      RSqlStatement myStatement;

    3. Define the indices to be used in the search:

      TInt nameIndex = myStatement.ColumnIndex(kName); -TInt populationIndex = myStatement.ColumnIndex(kPopulation);

    4. Set the 32-bit integer value for the SQL parameter 'value':

      TInt parameterIndex = myStatement.ParameterIndex(kVal); -err = myStatement.BindInt(parameterIndex,10);

      The SQL parameter to which the integer is being assigned is identified by the constant kVal from:

      _LIT(kVal,":Value"); -... -...WHERE population > :Value")

      The parameter plus constant, along with other parts of the statement, are converted into:

      in SQL syntax.

    5. Prepare the statement:

      TInt err; -err = myStatement.Prepare(countriesDatabase,kQueryString);

      This creates a parameterised SQL statement executable.

  2. Run the SQL query:

    1. Search the records until a match is found:

      while((err = myStatement.Next()) == KSqlAtRow) - { - Do something with the query results - }

      Next() fires the executable SQL statement and stops at and returns the matched record.

      Do something if no results are found.

      if(err == KSqlAtEnd) - <OK - no more records>; -else - <process the error>;

  3. The query is done and you have the results. In this section we look at a simple way to do something with the results and we close the SQL statement object.

    1. Get the results of the search:

      TPtrC myData; -myData = myStatement.ColumnTextL(nameIndex); -RDebug::Print(_L("Name=%d\n"), myData);

    2. Close the SQL search statement:

      err = myStatement.Close();

      When the database search is finished the object should be closed to free up resources.

Now that you have performed a basic database query you can start thinking about more advanced querying options. The following will show you how:

  • Querying Databases: Basic

  • Reading to a buffer

  • Reading to memory

  • Reading to a data stream

SQL Overview Inserting a row into a - table Deleting rows from a - table Reading to a - buffer Reading to memory Reading to a data - stream Writing to a data - stream Scalar queries \ No newline at end of file + + + + + +Querying +a databaseThis tutorial shows you how to create a simple SQL database query. +
Introduction

This +tutorial shows you how to wrap a SQL query statement into an RSqlStatement object +to query a database.

The SQL statement used for the tutorial is shown +here:

SELECT name FROM countries WHERE population > 10

The (SELECT) +results of the query will be the value in the 'name' column FROM the +'countries' table WHERE the value of the +'population' column of the same record is > the +value specified.

+
Procedure
    +

  1. Prepare the Statement:

    The +steps to prepare a SQL statement are shown here.

      +

    1. Set up some constants +used by the SQL statement object to define the SQL query:

      _LIT(kName,"name"); +_LIT(kPopulation,"population"); +_LIT(kVal,":Value"); +_LIT(kQueryString,"SELECT name FROM countries WHERE population > :Value");

      This +defines the query parameters.

      2. +

    2. Instantiate the RSqlStatement SQL +statement:

      RSqlStatement myStatement;

      3. +

    3. Define the indices to +be used in the search:

      TInt nameIndex = myStatement.ColumnIndex(kName); +TInt populationIndex = myStatement.ColumnIndex(kPopulation);

      4. +

    4. Set the 32-bit integer +value for the SQL parameter 'value':

      TInt parameterIndex = myStatement.ParameterIndex(kVal); +err = myStatement.BindInt(parameterIndex,10);

      The SQL +parameter to which the integer is being assigned is identified by the constant kVal from:

      _LIT(kVal,":Value"); +... +...WHERE population > :Value")

      The parameter plus constant, +along with other parts of the statement, are converted into:

      in SQL +syntax.

      5. +

    5. Prepare the statement:

      TInt err; +err = myStatement.Prepare(countriesDatabase,kQueryString);

      This +creates a parameterised SQL statement executable.

      6. +
    2. +

  2. Run the SQL query:

      +

    1. Search the records until +a match is found:

      while((err = myStatement.Next()) == KSqlAtRow) + { + Do something with the query results + }

      Next() fires the executable SQL statement and stops +at and returns the matched record.

      Do something if no results are +found.

      if(err == KSqlAtEnd) + <OK - no more records>; +else + <process the error>;

      2. +
    3. +

  3. The query is done and +you have the results. In this section we look at a simple way to do something +with the results and we close the SQL statement object.

      +

    1. Get the results of the +search:

      TPtrC myData; +myData = myStatement.ColumnTextL(nameIndex); +RDebug::Print(_L("Name=%d\n"), myData);

      2. +

    2. Close the SQL search +statement:

      err = myStatement.Close();

      When +the database search is finished the object should be closed to free up resources.

      3. +
    4. +

This section deals with finding and returning the first matching +record

only. Getting all matches in a database is briefly discussed +at the end of this

section.

+ +

Now that you have +performed a basic database query you can start thinking about more advanced +querying options. The following will show you how:

    +

  • Querying +Databases: Basic

    • +

  • Reading +to a buffer

    • +

  • Reading +to memory

    • +

  • Reading +to a data stream

    • +
+ +SQL Overview + +Inserting +a row into a table +Deleting +Rows from a Table +Reading to +a buffer +Reading to +memory +Reading to +a data stream +Writing to +a data stream +Scalar queries + + \ No newline at end of file