select: order_by limit

lib/rebel/sql.rb

@@ -13,13 +13,15 @@ module Rebel::SQL
     exec(Rebel::SQL.drop_table(table_name))
   end
 
-  def select(*fields, from: nil, where: nil, inner: nil, left: nil, right: nil)
+  def select(*fields, from: nil, where: nil, inner: nil, left: nil, right: nil, order_by: nil, limit: nil)
     exec(Rebel::SQL.select(*fields,
                            from: from,
                            where: where,
                            inner: inner,
                            left: left,
-                           right: right))
+                           right: right,
+                           order_by: order_by,
+                           limit: limit))
   end
 
   def insert_into(table_name, *rows)
@@ -178,13 +180,15 @@ module Rebel::SQL
       SQL
     end
 
-    def select(*fields, from: nil, where: nil, inner: nil, left: nil, right: nil)
+    def select(*fields, from: nil, where: nil, inner: nil, left: nil, right: nil, order_by: nil, limit: nil)
       <<-SQL
       SELECT #{names(*fields)} FROM #{name(from)}
       #{inner?(inner)}
       #{left?(left)}
       #{right?(right)}
-      #{where?(where)};
+      #{where?(where)}
+      #{order_by?(order_by)}
+      #{limit?(limit)};
       SQL
     end
 
@@ -304,10 +308,26 @@ module Rebel::SQL
       "#{name_or_value(l)} = #{name_or_value(r)}"
     end
 
+    def order(l, r)
+      "#{name(l)} #{value(raw(r.to_s))}"
+    end
+
     def assign_clause(clause)
       list(clause.map { |k, v| equal(k, v) })
     end
 
+    def order_by_clause(clause)
+      case clause
+      when Symbol, String
+        order_by_clause(name(clause) => nil)
+      when Hash
+        list(clause.map { |k, v| order(k, v) })
+      when Array
+        list(clause.map { |c| order_by_clause(c) })
+      else raise NotImplementedError, clause.class
+      end
+    end
+
     def clause_term(left, right)
       case right
       when Array
@@ -344,5 +364,13 @@ module Rebel::SQL
     def right?(join)
       join ? "RIGHT #{join}" : nil
     end
+
+    def order_by?(*clause)
+      clause.any? ? "ORDER BY #{order_by_clause(*clause)}" : nil
+    end
+
+    def limit?(count)
+      count ? "LIMIT #{count}" : nil
+    end
   end
 end

test/test_exec.rb

@@ -46,4 +46,21 @@ class TestExec < Minitest::Test
     insert_into :foo, id: 1, col: 'whatevs'
     assert_equal(select('*', from: :foo), [[1, 'whatevs']])
   end
+
+  def test_limit
+    create_table :foo, id: 'INT', col: 'VARCHAR(255)'
+    insert_into :foo, id: 1, col: 'whatevs'
+    insert_into :foo, id: 2, col: 'something else'
+    assert_equal(select('*', from: :foo, limit: 1), [[1, 'whatevs']])
+  end
+
+  def test_order_by
+    create_table :foo, id: 'INT', col: 'VARCHAR(255)', value: 'VARCHAR(255)'
+    insert_into :foo, id: 1, value: '2', col: 'whatevs'
+    insert_into :foo, id: 2, value: '2', col: 'something'
+    insert_into :foo, id: 3, value: '1', col: 'else'
+    assert_equal(select(:id, from: :foo, order_by: :col), [[3], [2], [1]])
+    assert_equal(select(:id, from: :foo, order_by: {id: :desc}), [[3], [2], [1]])
+    assert_equal(select(:id, from: :foo, order_by: [value: :asc, id: :asc]), [[3], [1], [2]])
+  end
 end