Dapper map multiple joins Sql Query

Question

I want to map complex object to dapper result from query which has two inner joins. I know we\'ve solution to map one inner join but I want to map two inner joins result.

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Answer 1

I decided to use Dapper to get a big data for calculating somethings. This is my dapper extension method to join 3 table in _RepositoryBase.cs file.

    public List<Tuple<T, T2, T3, T4>> QueryMultiple<T2, T3, T4>(string sql, object param)
        where T2 : class
        where T3 : class
    {
        using (var con = new SqlConnection(GetConnStr()))
        {
            if (con.State == ConnectionState.Closed)
                con.Open();

            var query = con.Query<T, T2, T3, T4, Tuple<T, T2, T3, T4>>(sql, (t, t2, t3, t4) => Tuple.Create(t, t2, t3, t4), param);

            //if (query.Count() == 0)
            //    return new List<T>();

            var data = query.ToList();

            con.Close();
            con.Dispose();

            return data;
        }
    }

Then, this function will help you to get sql joined data via dapper.

    public List<Table1> GetSqlJoinedDataViaDaper(int customerId)
    {
        var repo = new GenericRepository<T_LOOKUP>();
        var sql = @"select table1.ID Table1ID, table1.*,
                    table2.ID Table2ID, table2.*,
                    table3.ID Table3ID, table3.*
                    from dbo.Table1 table1 (nolock)
                    left outer join dbo.Table2 table2 (nolock) on table2.ID=table1.FKTable2ID
                    left outer join dbo.Table3 table3 (nolock) on table3.ID=table1.FKTable3ID
                    where table1.CustomerID=@p1 ";

        var resultWithJoin = repo.QueryMultiple<Table1, Table2, Table3>(sql,
            new { p1 = 1, splitOn = "Table1ID,Table2ID,Table3ID" }).ToList();

        var retval = new List<Table1>();
        foreach (var item in resultWithJoin)
        {
            Table1 t1 = item.Item2; //After first split
            t1.Table2 = item.Item3; //After Table2ID split
            t1.Table3 = item.Item4; //After Table3ID split

            retval.Add(t1);
        }
        return retval;
    }

Summary: Write your select and insert split between tables. Say splits to Dapper and get your data. I used this and worked better than Entity Framework.

Answer 2

I don't know what is class 'OrderDetail' you don't provide it so I used Order class.
This can also be done by QueryMultiple but because your question includes INNER JOIN I don't use it.

public Dictionary<int, Order> GetOrderLookup()
{
    var lookup = new Dictionary<int, Order>();

    const string sql = @"   SELECT  o.id,
                                    o.order_reference,
                                    o.order_status,

                                    ol.id,
                                    ol.order_id,
                                    ol.product_number,

                                    ols.id,
                                    ols.order_line_id,
                                    ols.size_name
                            FROM    orders_mstr o
                            JOIN    order_lines ol ON o.id = ol.order_id
                            JOIN    order_line_size_relations ols ON ol.id = ols.order_line_id";

    List<Order> orders = null;
    using (var connection = OpenConnection(_connectionString))
    {
        orders = connection.Query<Order, OrderLine, OrderLineSize, Order>(sql, (order, orderLine, orderLizeSize) =>
        {
            orderLine.OrderLineSizes = new List<OrderLineSize> { orderLizeSize };
            order.OrderLines = new List<OrderLine>() { orderLine };
            return order;
        },
        null, commandType: CommandType.Text).ToList();
    }

    if (orders == null || orders.Count == 0)
    {
        return lookup;
    }

    foreach (var order in orders)
    {
        var contians = lookup.ContainsKey(order.id);
        if (contians)
        {
            var newLinesToAdd = new List<OrderLine>();
            var existsLines = lookup[order.id].OrderLines;
            foreach (var existsLine in existsLines)
            {
                foreach (var newLine in order.OrderLines)
                {
                    if (existsLine.id == newLine.id)
                    {
                        existsLine.OrderLineSizes.AddRange(newLine.OrderLineSizes);
                    }
                    else
                    {
                        newLinesToAdd.Add(newLine);
                    }
                }
            }
            existsLines.AddRange(newLinesToAdd);
        }
        else
        {
            lookup.Add(order.id, order);
        }
    }

    return lookup;
}

Answer 3

I tried my best and solve it.

Here is the more easy and accurate solution as per me.:

var lookup = new Dictionary<int, OrderDetail>();
            var lookup2 = new Dictionary<int, OrderLine>();
            connection.Query<OrderDetail, OrderLine, OrderLineSize, OrderDetail>(@"
                    SELECT o.*, ol.*, ols.*
                    FROM orders_mstr o
                    INNER JOIN order_lines ol ON o.id = ol.order_id
                    INNER JOIN order_line_size_relations ols ON ol.id = ols.order_line_id           
                    ", (o, ol, ols) =>
            {
                OrderDetail orderDetail;
                if (!lookup.TryGetValue(o.id, out orderDetail))
                {
                    lookup.Add(o.id, orderDetail = o);
                }
                OrderLine orderLine;
                if (!lookup2.TryGetValue(ol.id, out orderLine))
                {
                    lookup2.Add(ol.id, orderLine = ol);
                    orderDetail.OrderLines.Add(orderLine);
                }
                orderLine.OrderLineSizes.Add(ols);
                return orderDetail;
            }).AsQueryable();

            var resultList = lookup.Values.ToList();