I think the Erlang Record structure would be an interesting way to contruct SQL queries. Each record would represent a type of query (#select, #update, #delete, etc), and the attributes within each would represent the different clauses of the query:

The simple example:

#select{
    fields=[username, email],
    from=user,
    where={userid, Userid},
}

This presents all kinds of potential issues, however.

• How to represent and or or in where clauses. I'm feeling prefix notation for that: {'or', [{email, Email}, {username, Username}]}
• How about joins? Listing the tables in from as a list ([table1, table2, table3] then having to use the where clause to join is a bit nasty. Specifying a table as a 2 or 3-tuple as follows seems interesting:

#select{
    fields=[userid, username, email]
    from=[
        user,
        {inner, post, userid},
        {inner, thread, {thread@id, post@threadid}}
    ]
}

Would basically translate to Select userid, username, email from user inner join post using userid inner join thread on thread.id=post.threadid

Subqueries are simple here, using #select records in place of table names in queries, which can add to some interesting and convenient Erlang-based query composition without having to screw around with iolists and concatenation.

Anyway, food for thought!