Question

java如何用sql语句求平均值

已经连接上了数据库，但不知道用哪个类来执行sql语句。
Connection Ex1Con=null;
Statement Ex1Stmt=null;
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
Ex1Con = DriverManager.getConnection("jdbc:odbc:diago", "", "");
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
Ex1Stmt = Ex1Con.createStatement();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

try {
StdutempName = rs.getString("StudName");
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}

try {
rs = Ex1Stmt.executeQuery("select avg(English) from studbasicinfo");
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}

try {
while(rs.next())
{
System.out.println(rs.getString("English"));
};

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

Answer 1

一种是把数据全读出来，然后求平均值，二是直接用sql语句求平均值，显然，第二种要好

追问

第二种怎么弄啊

追答

你有学过sql查询语句吗？

如果给出String sql="select avg(grade) from table";类似的字符串，执行这条语句即可

看你上面的代码，感觉在用odbc连接数据库，怎么不用Jdbc呢?

Answer 2

Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:orcl", "scott","tiger");
Statement st = conn.createStatement();
ResultSet set = st.executeQuery(sql);//返回结果集
st.execute(sql);//返回boolean类型，是否成功。