Adds MultiColumn queries section

src/main/scala/doobie/DoobieLibrary.scala

@@ -15,6 +15,7 @@ object DoobieLibrary extends Library {
 
   override def sections: List[Section] = List(
     ConnectingToDatabaseSection,
-    SelectingDataSection
+    SelectingDataSection,
+    MultiColumnQueriesSection
   )
 }

src/main/scala/doobie/DoobieUtils.scala

@@ -1,7 +1,5 @@
 package doobie
 
-import java.util.UUID
-
 import doobie.Model._
 import doobie.imports._
 import doobie.free.{ drivermanager => FD }

src/main/scala/doobie/Model.scala

@@ -4,9 +4,13 @@ object Model {
 
   case class Country(code: String, name: String, population: Long, gnp: Option[Double])
 
+  case class Code(code: String)
+
+  case class CountryInfo(name: String, pop: Int, gnp: Option[Double])
+
   val countries = List(
     Country("DEU", "Germany", 82164700, Option(2133367.00)),
-    Country("ESP", "Spain", 39441700, Option(553223.00)),
+    Country("ESP", "Spain", 39441700, None),
     Country("FRA", "France", 59225700, Option(1424285.00)),
     Country("GBR", "United Kingdom", 59623400, Option(1378330.00)),
     Country("USA", "United States of America", 278357000, Option(8510700.00))

src/main/scala/doobie/MultiColumnQueriesSection.scala

@@ -0,0 +1,144 @@
+package doobie
+
+import doobie.DoobieUtils._
+import doobie.Model._
+import doobie.imports._
+import org.scalaexercises.definitions.Section
+import org.scalatest.{FlatSpec, Matchers}
+import shapeless.record._
+import shapeless.{::, HNil}
+
+/**
+  * So far, we have constructed queries that return single-column results. These results were mapped
+  * to Scala types. But how can we deal with multi-column queries?
+  *
+  * In this section, we'll see what alternatives '''doobie''' offers us to work with multi-column
+  * queries.
+  *
+  * As in previous sections, we'll keep working with the 'country' table:
+  * {{{
+  * code    name                      population    gnp
+  * "DEU"  "Germany"                    82164700    2133367.00
+  * "ESP"  "Spain"                      39441700          null
+  * "FRA"  "France",                    59225700    1424285.00
+  * "GBR"  "United Kingdom"             59623400    1378330.00
+  * "USA"  "United States of America"  278357000    8510700.00
+  * }}}
+  *
+  * @param name multi_column_queries
+  */
+object MultiColumnQueriesSection extends FlatSpec with Matchers with Section {
+
+  /**
+    * We can select multiple columns and map them to a tuple. The `gnp` column in our table is
+    * nullable so we’ll select that one into an `Option[Double]`.
+    */
+  def selectMultipleColumnsUsingTuple(res0: Option[Double]) = {
+
+    val (name, population, gnp) =
+      sql"select name, population, gnp from country where code = 'ESP'"
+        .query[(String, Int, Option[Double])]
+        .unique
+        .transact(xa)
+        .run
+
+    gnp should be(res0)
+  }
+
+  /**
+    * doobie automatically supports row mappings for atomic column types, as well as options,
+    * tuples, `HList`s, shapeless records, and case classes thereof. So let’s try the same query
+    * with an `HList`
+    */
+  def selectMultipleColumnsUsingHList(res0: String) = {
+
+    type CountryHListType = String :: Int :: Option[Double] :: HNil
+
+    val hlist: CountryHListType =
+      sql"select name, population, gnp from country where code = 'FRA'"
+        .query[CountryHListType]
+        .unique
+        .transact(xa)
+        .run
+
+    hlist.head should be(res0)
+  }
+
+  /**
+    * And with a shapeless record:
+    */
+  def selectMultipleColumnsUsingRecord(res0: Int) = {
+
+    type Rec = Record.`'name -> String, 'pop -> Int, 'gnp -> Option[Double]`.T
+
+    val record: Rec =
+      sql"select name, population, gnp from country where code = 'USA'"
+        .query[Rec]
+        .unique
+        .transact(xa)
+        .run
+
+    record('pop) should be(res0)
+  }
+
+  /**
+    * And again, mapping rows to a case class.
+    *
+    * {{{
+    * case class Country(code: String, name: String, population: Long, gnp: Option[Double])
+    * }}}
+    */
+  def selectMultipleColumnsUsingCaseClass(res0: String) = {
+
+    val country =
+      sql"select code, name, population, gnp from country where name = 'United Kingdom'"
+        .query[Country]
+        .unique
+        .transact(xa)
+        .run
+
+    country.code should be(res0)
+  }
+
+  /**
+    * You can also nest case classes, `HList`s, shapeless records, and/or tuples arbitrarily as long
+    * as the eventual members are of supported columns types. For instance, here we map the same set
+    * of columns to a tuple of two case classes:
+    *
+    * {{{
+    * case class Code(code: String)
+    * case class CountryInfo(name: String, pop: Int, gnp: Option[Double])
+    * }}}
+    */
+  def selectMultipleColumnsUsingNestedCaseClass(res0: String) = {
+
+    val (code, country) =
+      sql"select code, name, population, gnp from country where code = 'ESP'"
+        .query[(Code, CountryInfo)]
+        .unique
+        .transact(xa)
+        .run
+
+    country.name should be(res0)
+  }
+
+  /**
+    * And just for fun, since the `Code` values are constructed from the primary key, let’s turn the
+    * results into a `Map`. Trivial but useful.
+    */
+  def selectMultipleColumnsUsingMap(res0: String, res1: Option[CountryInfo]) = {
+
+    val notFoundCountry = CountryInfo("Not Found", 0, None)
+
+    val countriesMap: Map[Code, CountryInfo] =
+      sql"select code, name, population, gnp from country"
+        .query[(Code, CountryInfo)]
+        .list
+        .transact(xa)
+        .run
+        .toMap
+
+    countriesMap.getOrElse(Code("DEU"), notFoundCountry).name should be(res0)
+    countriesMap.get(Code("ITA")) should be(res1)
+  }
+}

src/main/scala/doobie/SelectingDataSection.scala

@@ -23,7 +23,7 @@ import org.scalatest.{FlatSpec, Matchers}
   * {{{
   * code    name                      population    gnp
   * "DEU"  "Germany"                    82164700    2133367.00
-  * "ESP"  "Spain"                      39441700     553223.00
+  * "ESP"  "Spain"                      39441700          null
   * "FRA"  "France",                    59225700    1424285.00
   * "GBR"  "United Kingdom"             59623400    1378330.00
   * "USA"  "United States of America"  278357000    8510700.00

src/test/scala/doobie/MultiColumnQueriesSectionSpec.scala

@@ -0,0 +1,67 @@
+package doobie
+
+import doobie.Model.CountryInfo
+import org.scalacheck.Shapeless._
+import org.scalaexercises.Test
+import org.scalatest.Spec
+import org.scalatest.prop.Checkers
+import shapeless.HNil
+
+class MultiColumnQueriesSectionSpec extends Spec with Checkers {
+
+  def `select multiple columns using tuple` = {
+    val validResult: Option[Double] = None
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingTuple _,
+        validResult :: HNil
+      )
+    )
+  }
+
+  def `select multiple columns using HList` = {
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingHList _,
+        "France" :: HNil
+      )
+    )
+  }
+
+  def `select multiple columns using Record` = {
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingRecord _,
+        278357000 :: HNil
+      )
+    )
+  }
+
+  def `select multiple columns using case class` = {
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingCaseClass _,
+        "GBR" :: HNil
+      )
+    )
+  }
+
+  def `select multiple columns using nested case class` = {
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingNestedCaseClass _,
+        "Spain" :: HNil
+      )
+    )
+  }
+
+  def `select multiple columns using map` = {
+    val validResult: Option[CountryInfo] = None
+    check(
+      Test.testSuccess(
+        MultiColumnQueriesSection.selectMultipleColumnsUsingMap _,
+        "Germany" :: validResult :: HNil
+      )
+    )
+  }
+}