support #$ interpolation for dynamic sql such as table names, order clause, etc

Love relate and the SqlResult parsing is much cleaner than anorm. One thing missing is #$ interpolation which is supported by anorm and slick. Its helpful for use cases like dynamic table names, order clauses, etc:

val accountId = 2
val orderCol = "foo"
val orderDir = "desc"
sql"select name, sum(foo) as foo, sum(bar) as bar from table where account_id = $account_id group by name order by #$orderCol #$orderDir" 

I have a quick and dirty commit which unblocks me for now, would remove this for official version if/when supported: https://github.com/xadrnd/relate/commit/40e176617280e836ab5a6c6a7babbef3e04a47e5

Thanks!

[pauldraper]

@rfranco, that is actually already implemented 😉 InterpolatedQuery is a MultiParameter, which is a Parameter.

---

@rbanikaz, see https://github.com/lucidsoftware/relate/wiki/Query-Interpolation#query-composition.

// interpolate (my preference)
val sql1 = sql"SELECT * FROM users"
val sql2 = sql"$sql1 LIMIT 5"

// concatenate
val sql3 = sql"SELECT * FROM users"
val sql4 = sql" LIMIT 5"
val sql5 = sql3 + sql4

(FYI, if for some reason you aren’t constructing your queries with literal strings, an arbitrary string can be converted to a query by calling .toSql on it. Of course, you should only do this with trusted data.)

I like this approach to interpolation, as it encodes the semantics of the data – text data, or SQL query – in the type. It avoids the “String as universal data type” smell, and it makes accidental SQL injection more difficult.

Let me know if you find this reasonable.

[rbanikaz]

Cool thanks! I didn’t know about the toSql, that’s helpful at least it covers the use case.

I do think the #$ is nice, I didn’t spend much time going through your codebase, but I will go ahead and submit the PR, it will be great if you take a look I will be happy to respond to comments…

Cheers!