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    <p>I never used Slick or ScalaQuery so it was quite an adventure to find out how to achieve this. Slick is very extensible, but the documentation on extending is a bit tricky. It might already exist, but this is what I came up with. If I have done something incorrect, please correct me.</p> <p>First we need to create a custom driver. I extended the <code>H2Driver</code> to be able to test easily.</p> <pre><code>trait CustomDriver extends H2Driver { // make sure we create our query builder override def createQueryBuilder(input: QueryBuilderInput): QueryBuilder = new QueryBuilder(input) // extend the H2 query builder class QueryBuilder(input: QueryBuilderInput) extends super.QueryBuilder(input) { // we override the expr method in order to support the 'As' function override def expr(n: Node, skipParens: Boolean = false) = n match { // if we match our function we simply build the appropriate query case CustomDriver.As(column, LiteralNode(name: String)) =&gt; b"(" super.expr(column, skipParens) b") as ${name}" // we don't know how to handle this, so let super hanle it case _ =&gt; super.expr(n, skipParens) } } } object CustomDriver extends CustomDriver { // simply define 'As' as a function symbol val As = new FunctionSymbol("As") // we override SimpleSql to add an extra implicit trait SimpleQL extends super.SimpleQL { // This is the part that makes it easy to use on queries. It's an enrichment class. implicit class RichQuery[T: TypeMapper](q: Query[Column[T], T]) { // here we redirect our as call to the As method we defined in our custom driver def as(name: String) = CustomDriver.As.column[T](Node(q.unpackable.value), name) } } // we need to override simple to use our version override val simple: SimpleQL = new SimpleQL {} } </code></pre> <p>In order to use it we need to import specific things:</p> <pre><code>import CustomDriver.simple._ import Database.threadLocalSession </code></pre> <p>Then, to use it you can do the following (I used the tables from the official Slick documentation in my example).</p> <pre><code>// first create a function to create a count query def countCoffees(supID: Column[Int]) = for { c &lt;- Coffees if (c.supID === supID) } yield (c.length) // create the query to combine name and count val coffeesPerSupplier = for { s &lt;- Suppliers } yield (s.name, countCoffees(s.id) as "test") // print out the name and count coffeesPerSupplier foreach { case (name, count) =&gt; println(s"$name has $count type(s) of coffee") } </code></pre> <p>The result is this:</p> <pre><code>Acme, Inc. has 2 type(s) of coffee Superior Coffee has 2 type(s) of coffee The High Ground has 1 type(s) of coffee </code></pre>
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    1. COIt works good now. Thank you very much!
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