How to send plain SQL queries (and retrieve results) using scala slick 3

Question

I am trying to make a class that has methods that can send and get data to an SQLite db using plain sql queries. This unfortunately does not work. I do not want to use the withSession implicit parts.

import slick.driver.SQLiteDriver.api._
import slick.lifted.TableQuery
import slick.jdbc.JdbcBackend.Database;
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent._
import ExecutionContext.Implicits.global

    class DBops {
  val db = Database.forURL("jdbc:sqlite:S:/testing/testdb.sql",driver = "org.sqlite.JDBC")

def getData(TableName: String):Future[(Int,Double,String)]={
    db.run(sql"""select * from $TableName """.as[(Int,Double,String)])

}

}

The following error is thrown:

type mismatch; found : slick.profile.SqlStreamingAction[Vector[(Int, Double, String)],(Int, Double, String),slick.dbio.Effect] required: slick.dbio.DBIOAction[(Int, Double, String),slick.dbio.NoStream,Nothing] DBops.scala

Solution 1

I realized I was missing a Seq in the return type:

def getData(TableName: String): Future[Seq[(Int,Double,String)]] = {
  db.run(sql"""SELECT * FROM $TableName """.as[(Int, Double, String)])
}

Solution 2

You can use sql"..." with any String content using #$tableName:

db.run(sql"SELECT * FROM #$tableName".as[(Int, Double, String)])

Please remember: don't ever take the tableName as a user input - otherwise, there is a great risk for SQL injection. The normal $value solves these problems for you.

Read Slick manual (http://slick.typesafe.com/doc/3.0.0/sql.html#splicing-literal-values)

... sometimes you need to splice literal values directly into the statement, for example to abstract over table names ... You can use #$ instead of $ in all interpolators for this purpose ...

Comments

[Kyle Balkissoon]

Won't be taking it as a user input this is backend only, Is there any way in slick to NOT have to predefine the column types?

[Matias Saarinen]

You mean the sql"select...".as[(String, Int)]? Since you're programming Scala it is very important that you determine the types beforehand - that's type safety. Basically you can use tuples with any "primitive types" or you can create your own implicit GetResult. Read more: slick.typesafe.com/doc/3.0.0/sql.html#result-sets Plus: I can't see any reason why you could not create a GetResult which would create a list by just calling rs.next over the result set but I could not find any reference for that.