java.sql.ResultSet

java.sql.ResultSet is an execution result set interface.

Description

A ResultSet object is a data table that represents a database result set, which is usually generated by executing a statement that queries the database.

A ResultSet object maintains a cursor that points to its current data row. The cursor is initially positioned before the first row. After the next method is called, the cursor is moved to the next row. If no more rows exist in the ResultSet object, false is returned. Therefore, the next method can be used in a while loop to traverse the ResultSet object.

A default ResultSet object cannot be updated and has a cursor that moves only in a forward direction. In this case, you can traverse the result set only once from the first row to the last row. However, a scrollable or updatable ResultSet object can be generated. As shown in the following example, con is a valid Connection object.

Statement st = con.createStatement(
                                      ResultSet.TYPE_SCROLL_INSENSITIVE,
                                      ResultSet.CONCUR_UPDATABLE);
       ResultSet rs = stmt.executeQuery("SELECT a, b FROM TAB1");
       // rs will be scrollable and updatable but will not show changes made by others.

The ResultSet interface provides getter methods, such as getBoolean and getLong, that can be used to retrieve column values from the current row. Values can be retrieved by using column indexes or column names. In general, using column indexes is more efficient. Columns are numbered starting from 1. To achieve maximum portability, the result set columns in each row must be read from left to right, and each column must be read only once.

For a getter method, the JDBC driver attempts to convert the underlying data into the Java type specified in the getter method and returns valid Java values.

Column names used as the input of getter methods are case-insensitive. If a getter method is called by using column names and several columns have the same name, the value of the first matching column is returned. The column name option is designed to be used when column names are used in the SQL query that generates the result set. For columns that are not explicitly named in the query, we recommend that you use column numbers. If column names are used, the developer can use the SQL AS clause to ensure that each name is referenced by only one column.

Methods