哪一个更快？ 查询1个实体，并在其他相关实体上进行往返？ 还是刚离开1次往返旅行？

Question

public class Item
{
    public int Id { get; set; }
    public string Description { get; set; }
    public decimal Price { get; set; }
    public decimal Cost { get; set; }
    public Department ItemDept { get; set; }
    public Category ItemCat { get; set; }
    public List<Supplier> Suppliers { get; set; }
    public List<Barcode> Barcodes { get; set; }
    public List<Discount> Discounts { get; set; }

}

Im using Dapper so my query is plain SQL talking to Sql Server 2008

how do I improve performance on this? assuming the query is get Item by Id(Primary key) which one is faster or better? - with one query full of joins(left join, inner join..etc) (1 roundtrip only) or - query the item first then execute another query for related tables(many roundtrips) or do you guys have any recommendations?

Answer 1

This is too long for a comment.

The best way to answer a performance question is to try it out on your data on your systems. You can then check what really works better.

Informed speculation says that letting the database do the joins is the right thing to do. Databases are designed for this operation and they should implement joins effectively. Perhaps more importantly, there is overhead for each query that you run. Overhead to compile the query. Latency is passing the query to the database. Database overhead in processing the results and getting them back to the application.

That also suggests that doing more work in the database is a good thing. But, you should check on your system.