11.4

对数据库的查询优化有了更深入的理解，使用索引优化查询
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JavaMySQLQueryOptimizationExample {
public static void main(String[] args) {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
Statement stmt = con.createStatement();
// 查询前查看执行计划
ResultSet explainResult = stmt.executeQuery("EXPLAIN SELECT * FROM mytable WHERE indexed_column = 'value'");
while (explainResult.next()) {
System.out.println(explainResult.getString(1) + " " + explainResult.getString(2));
}
// 执行查询
ResultSet rs = stmt.executeQuery("SELECT * FROM mytable WHERE indexed_column = 'value'");
while (rs.next()) {
System.out.println(rs.getString("column_name"));
}
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}