JDBC Result Sets (ResultSet)

The SQL statement that reads data from a database query returns data in the result set. The SELECT statement is the standard method for selecting rows from a database and viewing them in the result set. The Sql.ResultSet interface represents the result set of a database query.

The ResultSet object maintains a cursor pointing to the current row in the result set. The term 'result set' refers to the row and column data contained in the ResultSet object.

The methods of the ResultSet interface can be divided into three categories-

• Navigation methods: Used to move the cursor left and right.

• Get method: Used to view data in the columns of the current row pointed to by the cursor.

• Update method:Used to update data in each column of the current row. Then, the update can also be reflected in the underlying database.

The cursor can move according to the properties of the ResultSet. These properties are specified when creating the corresponding Statement that generates the ResultSet.

JDBC provides the following connection methods to create statements with the required ResultSet.-

• createStatement(int RSType, int RSConcurrency);

• prepareStatement(String SQL, int RSType, int RSConcurrency);

• prepareCall(String sql, int RSType, int RSConcurrency);

The first parameter represents the type of the ResultSet object, and the second parameter is one of the two ResultSet constants, used to specify whether the result set is read-only or updatable.

Type of result set

Concurrency of ResultSet

Possible RSConcurrency is given below. If you do not specify any concurrency type, you will automatically obtain the CONCUR_READ_ONLY type.

So far, all the examples we have written can be written as follows, which initializes a Statement object to create a read-only ResultSet object-

try　{
　　　Statement　stmt　=　conn.createStatement(
　　　　　　　　　　　　　　　　　　　　　　　　　　　ResultSet.TYPE_FORWARD_ONLY,
　　　　　　　　　　　　　　　　　　　　　　　　　　　ResultSet.CONCUR_READ_ONLY);
}
catch(Exception　ex)　{
　　　....
}
finally　{
　　　....
}

Navigating the result set

There are several methods involving cursor movement in the ResultSet interface, including-

To better understand, let's study "Navigation-Sample code.

View result set

The ResultSet interface contains many methods for obtaining data in the current row.

Each possible data type has a get method, and each get method has two versions-

• A column with a column name.

• An index with a column index.

For example, if the column you are interested in viewing contains an int, you need to use one of the getInt() methods of ResultSet.

Similarly, in the ResultSet interface, for each of the eight Java basic types, as well as common types (such as java.lang.String, java.lang.Object, and java.net.URL), there is a get method.

There are also methods to obtain SQL data types java.sql.Date, java.sql.Time, java.sql.Timestamp, java.sql.Clob, and java.sql.Blob. View the documentation for more information on using these SQL data types.

To better understand, let's studyView-Example Code.

Update result set

The ResultSet interface contains a collection of update methods used to update the result set data.

Like the get method, each data type has two update methods.-

• A column with a column name.

• An index with a column index.

For example, to update the current row's String column in the result set, you can use one of the following updateString() methods.-

There are eight primitive data types and update methods for String, Object, URL, and SQL data types in the java.sql package.

Updating a row in the result set changes the columns of the current row in the ResultSet object but does not change the row in the underlying database. To update changes to a row in the database, you need to call one of the following methods.

To better understand, let's study "Update Example Code.