How to get the sum of numeric column in Ent-CodePudding

I have two tables: products and baskets, which have the M2M relation and the table name is basket_products. I am trying to get the specific basket-related products total price and quantity, but I am getting stuck again. How can I fix the following code to get the result? note: I am using the Ent framework

   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)

CodePudding user response：

Did you try changing GroupBy("price") to GroupBy(Basket.FieldPrice) i.e. referencing the fields by generated field name. The example Group By Edge should be similar https://entgo.io/docs/aggregate/

CodePudding user response：

The Aggregate and GroupBy functions are the friends. Aggregation | Ent

I modified the code as given below and got a very optimized SQL query, thanks to the Ent team.

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)

The generated SQL:

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]