1.1.1 查询多条记录
@Test
/**
* 查询多条记录
*/
public void demo4(){
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try{
// 注册驱动
Class.forName("com.mysql.jdbc.Driver");
// 获得连接
conn = DriverManager.getConnection("jdbc:mysql:///web_test3", "root", "abc");
// 执行操作
// 创建执行SQL语句的对象:
stmt = conn.createStatement();
// 编写SQL:
String sql = "select * from user";
// 执行SQL:
rs = stmt.executeQuery(sql);
// 遍历结果集:
while(rs.next()){
System.out.println(rs.getInt("id")+" "+rs.getString("username")+" "+rs.getString("password"));
}
}catch(Exception e){
e.printStackTrace();
}finally{
// 资源释放：
if(rs != null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
if(stmt != null){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
conn = null;
}
}
}
1.1.2 查询一条记录
@Test
/**
* 查询一条记录
*/
public void demo5(){
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try{
// 注册驱动
Class.forName("com.mysql.jdbc.Driver");
// 获得连接
conn = DriverManager.getConnection("jdbc:mysql:///web_test3", "root", "abc");
// 执行SQL
// 创建执行SQL语句对象:
stmt = conn.createStatement();
// 编写SQL:
String sql = "select * from user where id = 4";
rs = stmt.executeQuery(sql);
// 判断就可以:
if(rs.next()){
System.out.println(rs.getInt("id")+" "+rs.getString("username")+" "+rs.getString("password"));
}
}catch(Exception e){
e.printStackTrace();
}finally{
// 资源释放：
if(rs != null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
if(stmt != null){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
conn = null;
}
}
}