ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with local SQL databases in AIR
Defining the data type of SELECT result data
Adobe AIR 1.0 and later
By default, each row returned by a SELECT statement is created as an Object instance with properties named for the
result set's column names and with the value of each column as the value of its associated property. However, before
executing a SQL SELECT statement, you can set the itemClass property of the SQLStatement instance to a class. By
setting the itemClass property, each row returned by the SELECT statement is created as an instance of the designated
class. The runtime assigns result column values to property values by matching the column names in the SELECT result
set to the names of the properties in the itemClass class.
Any class assigned as an itemClass property value must have a constructor that does not require any parameters. In
addition, the class must have a single property for each column returned by the SELECT statement. It is considered an
error if a column in the SELECT list does not have a matching property name in the itemClass class.
Retrieving SELECT results in parts
Adobe AIR 1.0 and later
By default, a SELECT statement execution retrieves all the rows of the result set at one time. Once the statement
completes, you usually process the retrieved data in some way, such as creating objects or displaying the data on the
screen. If the statement returns a large number of rows, processing all the data at once can be demanding for the
computer, which in turn will cause the user interface to not redraw itself.
You can improve the perceived performance of your application by instructing the runtime to return a specific number
of result rows at a time. Doing so causes the initial result data to return more quickly. It also allows you to divide the
result rows into sets, so that the user interface is updated after each set of rows is processed. Note that it’s only practical
to use this technique in asynchronous execution mode.
To retrieve SELECT results in parts, specify a value for the SQLStatement.execute() method’s first parameter (the
prefetch parameter). The prefetch parameter indicates the number of rows to retrieve the first time the statement
executes. When you call a SQLStatement instance’s execute() method, specify a prefetch parameter value and only
that many rows are retrieved:
var stmt:SQLStatement = new SQLStatement();
stmt.sqlConnection = conn;
stmt.text = "SELECT ...";
stmt.addEventListener(SQLEvent.RESULT, selectResult);
stmt.execute(20); // only the first 20 rows (or fewer) are returned
The statement dispatches the result event, indicating that the first set of result rows is available. The resulting
SQLResult instance’s data property contains the rows of data, and its complete property indicates whether there are
additional result rows to retrieve. To retrieve additional result rows, call the SQLStatement instance’s next() method.
Like the execute() method, the next() method’s first parameter is used to indicate how many rows to retrieve the
next time the result event is dispatched.
Last updated 6/6/2012
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