JDBC ResultSet Interface
The ResultSet interface within java.sql functions to store query results from databases when executing commands like SELECT statements. The ResultSet functions as a cursor that points to a single data row and enables extracting values from columns.
Key Responsibilities
- Hold tabular data returned from queries
- Navigate rows using a cursor
- Fetch values from every column within the active row.
Package
import java.sql.ResultSet;
Syntax
Statement stmt = connection.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM employees");
Methods of ResultSet
| Method | Description |
|---|---|
| next() | Moves the cursor to the next row |
| previous() | Moves to the previous row |
| first() | Moves to the first row |
| last() | Moves to the last row |
| absolute(int row) | Moves to a specific row |
| beforeFirst() | Moves to before the first row |
| afterLast() | Moves to after the last row |
| isBeforeFirst() | Checks if before first row |
| isAfterLast() | Checks if after last row |
Example
import java.sql.*;
public class ResultSetExample {
public static void main(String[] args) {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/testdb", "root", "password");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM employees");
// Process result set
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
double salary = rs.getDouble("salary");
System.out.println(id + " - " + name + " - " + salary);
}
rs.close();
stmt.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Best Practices
- Always close ResultSet after use.
- Use column names for clarity and maintainability.
- Scrollable and updatable SQL types require additional memory resources and processing power.
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