从一个表返回数据以及从另一个表映射数据的SQL最佳方法

Question

I have the following problem.

I have a table Entries that contains 2 columns:

• EntryID - unique identifier
• Name - some name

I have another EntriesMapping table ( many to many mapping table) that contains 2 columns :

• EntryID that refers to the EntryID of the Entries table
• PartID that refers to a PartID in a seprate Parts table.

I need to write a SP that will return all data from Entries table, but for each row in the Entries table I want to provide a list of all PartID 's that are registered in the EntriesMapping table.

My question is how do I best approach the deisgn of the solution to this, given that the results of the SP would regularly be processed by an app so performance is quite important.

1. Do I write a SP that will select multiple rows per entry - where if there are more than one PartID 's registered for a given entry - I will return multiple rows each having the same EntryID and Name but different PartID 's

OR

2. Do I write a SP that will select 1 row per entry in the Entries table, and have a field that is a string/xml/json that contains all the different PartID 's.

OR

3. There is some other solution that I am not thinking of?

Solution 1 seems to me to be the better way to go, but I will be passing lots of repeating data.

Solution 2 wont pass extra data, but the string/json/xml would need to be processed additionally, resuling in larger cpu time per item.

PS: I feel like this is quite a common problem to solve, but I was unable to find any resource that can provide common solutions or some pros/cons to different approaches.

Answer 1

I think you need simple JOIN :

SELECT e.EntryId, e.Name, em.PartId
FROM Entries e
JOIN EntriesMapping em ON e.EntryId = em.EntryId

This will return what you want, no need for stored procedure for that.