Question

I’m trying to generate a SQL query that can join two tables together and return the result .. but the second table is ‘flattened’. I’m not sure if that’s the correct technical term. Is it denormalized?

Anyways, can someone suggest how I could do this?

Table: Users

UserId  Name
1       Pure.Krome
2       John
3       Jill
4       Jane

Table: UserAliases

UserAliasId  UserId  Alias
1            1       Idiot
2            1       PewPew
3            3       BlahBlahBlah

Desired results

UserId  Name        Aliases
1       Pure.Krome  Idiot PewPew
2       John
3       Jill        BlahBlahBlah
4       Jane

Please note:

• A user does NOT need to have an alias. So that’s a zero->many relationship (outer join)
• The delimiter for the flattening of the 2nd table is a SPACE. If an alias has a space, bad luck for me. (Consider it, bad data).

Another example of my problem is to think of a StackOverflow question + tags.

Answer 1

FOR XML PATH is handy in this situation:

SELECT UserID, Name 
    , LTRIM(RTRIM((SELECT ' ' + Alias 
        FROM UserAliases WHERE UserID = u.UserID 
        FOR XML PATH('')))) AS Aliases
FROM Users u