MySQL数据库和Go语言：如何进行数据分组处理？

CREATE TABLE sales (
  id INT UNSIGNED NOT NULL AUTO_INCREMENT,
  product_id INT UNSIGNED NOT NULL,
  date DATE NOT NULL,
  amount DECIMAL(10,2) NOT NULL,
  PRIMARY KEY (id)
);

SELECT product_id, date, SUM(amount) AS total_amount
FROM sales
GROUP BY product_id, date;

import (
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/db_name")
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    rows, err := db.Query("SELECT product_id, date, SUM(amount) AS total_amount FROM sales GROUP BY product_id, date")
    if err != nil {
        panic(err.Error())
    }
    defer rows.Close()

    for rows.Next() {
        var productID int
        var date string
        var totalAmount float64
        if err := rows.Scan(&productID, &date, &totalAmount); err != nil {
            panic(err.Error())
        }
        fmt.Printf("Product ID: %d, Date: %s, Total Amount: %.2f
", productID, date, totalAmount)
    }
    if err := rows.Err(); err != nil {
        panic(err.Error())
    }
}