mysql - 使用 JDBC 对数据进行分组

Question

有没有办法在两个节点中使用 group by 函数，但作为通过 JDBC 连接的一个结果，有一个选项可以设置一个备份节点，但我们想在 2 个服务器上设置 group by 函数以获得一个查询，这里是 spark有 jdbc 连接

port_82 = "jdbc:mysql://******:**/packetlogic"
port_85 = "jdbc:mysql://******:**/packetlogic"
properties = {
    "user": "**",
    "password": "**",
    "driver": "",
    "ConnectionLoadBalance": 1
}

df =spark.read.format("JDBC").options(
    url = port_82,
    query = "select SUM(A),SUM(B),AVG(C),D,C FROM T WHERE ***** GROUP BY D,C  ",
    **properties
).load()

Answer 1

首先，创建表并像这样插入记录: 并编写如下代码:

Create table EMP (name varchar(12),id int(5),salary int(10));
INSERT INTO EMP(name,id,salary) VALUES("Arun",1,2500 );
INSERT INTO EMP(name,id) VALUES("Dinesh",3 );
INSERT INTO EMP(name,id,salary) VALUES("Karthik",3,5000 );
INSERT INTO EMP(name,id,salary) VALUES("Tamil",4,2500 );

public static void main(String[] args) throws Exception {

    Class.forName("com.mysql.jdbc.Driver").newInstance();
    Connection conn = DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/Arun", "root", "root");
    Statement st = conn.createStatement();

    st = conn.createStatement();
    ResultSet rs = st
            .executeQuery("  SELECT name,SUM(salary)from Emp GROUP BY name");

    while (rs.next()) {
        String name = rs.getString(1);
        String salary = rs.getString(2);
        System.out.println(name);
        System.out.println(salary);

    }

    rs.close();
    st.close();
    conn.close();