JDBC Result Sets

JDBC - Result Sets

This tutorial is basically about the JDBC Result sets.The main concept of the result sets is that the SQL statements that generally read the data from a database query is known to return the data in a result set. The standard way to select rows from a database and view them in a result set is known as the SELECT statement. The java.sql.ResultSet interface is usually used to represent the result set of a database query.

A ResultSet object in the JDBC is known to maintain a cursor that generally points towards the current row in the result set. In simple terms the "result set" generally refers to the row and column data that is possessed by a ResultSet object.

• Navigational methods : This method is basically used in order to move the cursor around.
• Get methods : This method is basically used in order to view the data in the columns of the current row that is being pointed by the cursor.
• Update methods : This method is basically used in order to update the data in the columns of the current row. The updates that are made can be then updated in the underlying database as well.

The cursor is generally known to be movable based on the properties of the ResultSet. These properties are basically designated whenever the corresponding Statement that is being generated, the ResultSet is created.

• createStatement(int RSType, int RSConcurrency);
• prepareStatement(String SQL, int RSType, int RSConcurrency);
• prepareCall(String sql, int RSType, int RSConcurrency);

The first argument that has been mentioned is basically used to indicate the type of a ResultSet object then the second argument is basically the one of two ResultSet constants that is used for specifying whether a result set is read-only or updatable.

Type of Result Set

In case the programmer does not specify any ResultSet type then the programmer will automatically get one that is TYPE_FORWARD_ONLY.

Here are the possible RSType are mentioned below:

Concurrency of ResultSet

In case the programmer does not specify any Concurrency type then the programmer will automatically get one that is CONCUR_READ_ONLY. Here are the possible RSConcurrency are mentioned below:

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

Navigating a Result Set

There are numerous methods in the ResultSet interface that is known to involve moving of the cursor that are depicted below along with a brief description:

Viewing a Result Set

The ResultSet interface in the JDBC is generally known to contain dozens of methods for getting the data of the current row.

There is basically a get method for each of the data types that are possible and each of the get method generally has two versions that are depicted below:

• One version is that takes in a column name.
• One version is that takes in a column index.

For instance, in case the column in which the user is interested in viewing is containing an int, then the programmer will need to use one of the getInt() methods of ResultSet that are explained below:

Correspondingly, there are get methods that are present in the ResultSet interface for each of the eight Java primitive types and they are also known to be present for the common types like java.lang.Object, java.lang.String, and java.net.URL.

Apart from that there are also some methods that are in order to get the SQL data types like java.sql.Time, java.sql.TimeStamp, java.sql.Date, java.sql.Clob, and the java.sql.Blob. It is recommended to check the documentation in order to get more information about the use of these SQL data types.

Updating a Result Set

The ResultSet interface is generally known to consist of a collection of update methods that are used for updating the data of a result set.

Likewise of the get methods, there are also the two update methods for each of the data types that are mentioned below:

• One version is that takes in a column name.
• One version is that takes in a column index.

For instance, in order to update a String column of the current row of a result set the user have to use one of the following updateString() methods that are described below along with a brief description:

In JDBC, there are generally update methods for each of the eight primitive data types and these methods also imply on String, Object, URL, and the SQL data types that are present in the java.sql package.

Updating a row in the result set means that it will definitely change the columns of the current row in the ResultSet object but this will not make any changes in the underlying database. In order to update the changes that have been made by the programmer to the row in the database, the programmer will need to invoke one of the below mentioned methods: