Make SqlWithParams composable

rdbc-api-scala/src/main/scala/io/rdbc/sapi/SqlInterpolatorTrait.scala

@@ -27,8 +27,8 @@ trait SqlInterpolatorTrait {
       *  val select = conn.select(sql"select * from test where id = \$id")
       * }}}
       *
-      * The code above produces `select * from test where id = :p1` statement
-      * with `p1` parameter bound to value `10`.
+      * The code above produces `select * from test where id = ?` statement
+      * with the sole parameter bound to value `10`.
       *
       * The interpolator supports also literal values that allow to dynamically
       * construct statements. To use this feature, instead of \$, use #\$,
@@ -40,24 +40,22 @@ trait SqlInterpolatorTrait {
       *  val select = conn.select(sql"select * from #\$table where id = \$id")
       * }}}
       *
-      * The code above produces `select * from test where id = :p1` statement
-      * with `p1` parameter bound to value `10`.
+      * The code above produces `select * from test where id = ?` statement
+      * with the sole parameter bound to value `10`.
       */
     def sql(args: Any*): SqlWithParams = {
       sc.checkLengths(args)
 
       var sqlArgs = Vector.empty[Any]
       val argsIter = args.iterator
-      var sqlArgIdx = 1
       val sql = new StringBuilder
 
       sc.parts.foreach { part =>
         if (part.endsWith("#") && argsIter.hasNext) {
           sql.append(part.take(part.length - 1))
           sql.append(argsIter.next)
         } else if (argsIter.hasNext) {
-          sql.append(part).append(":p").append(sqlArgIdx)
-          sqlArgIdx += 1
+          sql.append(part).append("?")
           sqlArgs = sqlArgs :+ argsIter.next
         } else {
           sql.append(part)

rdbc-api-scala/src/main/scala/io/rdbc/sapi/SqlWithParams.scala

@@ -26,5 +26,22 @@ import io.rdbc.ImmutIndexedSeq
   *   val id = 0
   *   val s: SqlWithParams = sql"select * from test where id = \$id"
   * }}}
+  *
+  * Instances created by the interpolator can be composed:
+  * {{{
+  *   import io.rdbc.sapi._
+  *   val x = 0
+  *   val y = 0
+  *   val s: SqlWithParams =
+  *     sql"select * from test where x = \x" +
+  *     sql"and y = $y"
+  * }}}
   */
-case class SqlWithParams(sql: String, params: ImmutIndexedSeq[Any])
+case class SqlWithParams(sql: String, params: ImmutIndexedSeq[Any]) {
+  def +(other: SqlWithParams): SqlWithParams = {
+    copy(
+      sql = sql + other.sql,
+      params = params.toVector ++ other.params
+    )
+  }
+}