A ResultSet object maintains a cursor pointing
to its current row of data. Initially the cursor is positioned
before the first row. The next method moves the
cursor to the next row, and because it returns false
when there are no more rows in the ResultSet object,
it can be used in a while loop to iterate through
the result set.
A default ResultSet object is not updatable and
has a cursor that moves forward only. Thus, you can
iterate through it only once and only from the first row to the
last row. It is possible to
produce ResultSet objects that are scrollable and/or
updatable. The following code fragment, in which con
is a valid Connection object, illustrates how to make
a result set that is scrollable and insensitive to updates by others, and
that is updatable. See ResultSet fields for other
Statement stmt = con.createStatement(
ResultSet rs = stmt.executeQuery("SELECT a, b FROM TABLE2");
// rs will be scrollable, will not show changes made by others,
// and will be updatable
For the getter methods, a JDBC driver attempts
to convert the underlying data to the Java type specified in the
getter method and returns a suitable Java value. The JDBC specification
has a table showing the allowable mappings from SQL types to Java types
that can be used by the ResultSet getter methods.
Column names used as input to getter methods are case
insensitive. When a getter method is called with
a column name and several columns have the same name,
the value of the first matching column will be returned.
The column name option is
designed to be used when column names are used in the SQL
query that generated the result set.
For columns that are NOT explicitly named in the query, it
is best to use column numbers. If column names are used, the
programmer should take care to guarantee that they uniquely refer to
the intended columns, which can be assured with the SQL AS clause.
A set of updater methods were added to this interface
in the JDBC 2.0 API (JavaTM 2 SDK,
Standard Edition, version 1.2). The comments regarding parameters
to the getter methods also apply to parameters to the
The updater methods may be used in two ways:
rs.absolute(5); // moves the cursor to the fifth row of rs
rs.updateString("NAME", "AINSWORTH"); // updates the
// NAME column of row 5 to be AINSWORTH
rs.updateRow(); // updates the row in the data source
rs.moveToInsertRow(); // moves cursor to the insert row
rs.updateString(1, "AINSWORTH"); // updates the
// first column of the insert row to be AINSWORTH
rs.updateInt(2,35); // updates the second column to be 35
rs.updateBoolean(3, true); // updates the third column to true
A ResultSet object is automatically closed when the
Statement object that
generated it is closed, re-executed, or used
to retrieve the next result from a sequence of multiple results.
The number, types and properties of a ResultSet
object's columns are provided by the ResulSetMetaData
object returned by the ResultSet.getMetaData method.