Minor cleanup

lib/dialects/abstract/query-generator.js

@@ -483,6 +483,10 @@ module.exports = (function() {
       mainAttributes = mainAttributes && mainAttributes.map(function(attr){
         var addTable = true
 
+        if (attr instanceof Utils.literal) {
+          return attr.toString(this)
+        }
+
         if (attr instanceof Utils.fn || attr instanceof Utils.col) {
           return self.quote(attr)
         }
@@ -592,10 +596,11 @@ module.exports = (function() {
               if (subQuery) {
                 if (!options.where) options.where = {}
 
-                var _where = "(SELECT "+self.quoteIdentifier(identSource)+" FROM " + self.quoteIdentifier(throughTable) + " AS " + self.quoteIdentifier(throughAs);
-                _where += joinType + self.quoteIdentifier(table) + " AS " + self.quoteIdentifier(as) + " ON ";
-                _where += targetJoinOn;
-                _where += " WHERE " + sourceJoinOn + " AND " + targetWhere + " LIMIT 1)";
+                var _where = "(";
+                  _where += "SELECT "+self.quoteIdentifier(identSource)+" FROM " + self.quoteIdentifier(throughTable) + " AS " + self.quoteIdentifier(throughAs);
+                  _where += joinType + self.quoteIdentifier(table) + " AS " + self.quoteIdentifier(as) + " ON "+targetJoinOn;
+                  _where += " WHERE " + sourceJoinOn + " AND " + targetWhere + " LIMIT 1"
+                _where += ")";
                 _where += " IS NOT NULL"
 
                 options.where["__"+throughAs] = self.sequelize.asIs(_where)