JDBC：增、删、改、查

查询因为要返回数据，所以和增删改不一样

增加

String sql = "insert into hero values(null, "+"'提莫'"+","+313.0f+","+50+")";

删除

String sql = "delete from hero where id=5";

修改

String sql = "update hero set name = 'name 5' where id = 3";

查询语句

• executeQuery执行SQL查询语句

String sql = "select * from hero";
ResultSet rs = s.executeQuery(sql);
while (rs.next()) {
        int id = rs.getInt("id");
        String name = rs.getString(2);
        float hp = rs.getFloat("hp");
        int damage = rs.getInt(4);
        System.out.printf("%d\t%s\t%f\t%d%n", id, name, hp, damage);
}

SQL语句判断账号密码是否正确

String name = "dashen";
String password = "thisispassword";
String sql = "select * from user where name = '" + name + "' and password = '" + password +"'";
ResultSet rs = s.executeQuery(sql);
if (rs.next()) 
    System.out.println("账号密码正确");
else 
    System.out.println("账号密码错误");   

获取总数

String sql = "select count(*) from hero";
ResultSet rs = s.executeQuery(sql);
int total = 0;
while (rs.next()) {
    total = rs.getInt(1);
}
System.out.println("表Hero中总共有：" + total + "条数据");

分页查询：Limit语句

• 设计一个方法，进行分页查询：public static void list(int start, int count)
• start是起始编号，count是数量

String sql = "select * from hero limit " + start + "," + count;