Go 如何获得Ent中数字列的总和

发布于04月10日

我有两个表:products和baskets，它们有M2M关系，表名是basket_products.我试图得到具体的篮子相关的products个总数和price个数量，但我再次陷入困境.如何修复以下代码以获得结果？注意:我使用的是Ent框架

   err = client.Basket.
        Query().
        Where(basket.ID(2)).
        WithProducts().
        QueryProducts().
        GroupBy("price").
        Aggregate(func(selector *sql.Selector) string {
            return sql.As(sql.Sum("price"), "price")
        }).Scan(ctx, &r)
    if err != nil {
        log.Println(err)
    }
    log.Println(r)

推荐答案

Aggregate和GroupBy功能是朋友.Aggregation | Ent

感谢Ent团队，我修改了下面给出的代码，得到了一个非常优化的SQL查询.

err := client.Basket.
        Query().
        Where(basketEntity.ID(ID)).
        GroupBy(basketEntity.FieldID).
        Aggregate(func(s *sql.Selector) string {
            t := sql.Table(product.Table)
            joinT := sql.Table(basketEntity.ProductsTable)
            s.Join(joinT).
                On(s.C(basketEntity.FieldID), joinT.C(basketEntity.ProductsPrimaryKey[0]))
            s.Join(t).
                On(t.C(product.FieldID), joinT.C(basketEntity.ProductsPrimaryKey[1]))
            return sql.As(sql.Sum(t.C(product.FieldPrice)), "price")
        }).
        Aggregate(repository.Count()).
        Scan(ctx, &report)

生成的SQL个:

SELECT "baskets"."id", SUM("t2"."price") AS "price", COUNT(*) 
FROM "baskets" 
JOIN "basket_products" AS "t1" ON "baskets"."id" = "t1"."basket_id" 
JOIN "products" AS "t2" ON "t2"."id" = "t1"."product_id" 
WHERE "baskets"."id" = $1 
GROUP BY "baskets"."id" args=[1]