Allow sorting on relations' columns

lib/sql.js

@@ -863,10 +863,24 @@ SQLConnector.prototype.buildOrderBy = function(model, order) {
   var clauses = [];
   for (var i = 0, n = order.length; i < n; i++) {
     var t = order[i].split(/[\s,]+/);
-    if (t.length === 1) {
-      clauses.push(self.columnEscaped(model, order[i]));
+    var colName;
+    if (t[0].indexOf('.') < 0) {
+      colName = self.columnEscaped(model, t[0]);
     } else {
-      clauses.push(self.columnEscaped(model, t[0]) + ' ' + t[1]);
+      // Column name is in the format: relationName.columnName
+      var colSplit = t[0].split('.');
+      // Find the name of the relation's model ...
+      var modelDef = this.getModelDefinition(model);
+      var relation = modelDef.model.relations[colSplit[0]];
+      var colModel = relation.modelTo.definition.name;
+      // ... and escape them
+      colName = self.columnEscaped(colModel, colSplit[1]);
+    }
+
+    if (t.length === 1) {
+      clauses.push(colName);
+    } else {
+      clauses.push(colName + ' ' + t[1]);
     }
   }
   return 'ORDER BY ' + clauses.join(',');

test/sql.test.js

@@ -364,6 +364,29 @@ describe('sql connector', function() {
     });
   });
 
+  it('builds SELECT with INNER JOIN and order by relation columns', function () {
+    var sql = connector.buildSelect('order', {
+      where: {
+        customer: {
+          fields: {
+            'name': true,
+            'vip': true
+          }
+        }
+      },
+      order: ['customer.vip DESC', 'customer.name ASC']
+    });
+
+    expect(sql.toJSON()).to.eql({
+      sql: 'SELECT DISTINCT `ORDER`.`ID`,`ORDER`.`DATE`,`ORDER`.`CUSTOMER_NAME`,' +
+      '`ORDER`.`STORE_ID` FROM `ORDER` INNER JOIN ( SELECT `CUSTOMER`.`NAME`,' +
+      '`CUSTOMER`.`VIP` FROM `CUSTOMER` ORDER BY `CUSTOMER`.`NAME` ) AS `CUSTOMER`' +
+      ' ON `ORDER`.`CUSTOMER_NAME`=`CUSTOMER`.`NAME`  ORDER BY ' +
+      '`CUSTOMER`.`VIP` DESC,`CUSTOMER`.`NAME` ASC',
+      params: []
+    });
+  });
+
   it('builds SELECT with multiple INNER JOIN', function () {
     var sql = connector.buildSelect('customer', {
       where: {