Fix bug (cause by required on N:M)

lib/dialects/abstract/query-generator.js

@@ -737,25 +737,26 @@ module.exports = (function() {
               joinQueryItem += sourceJoinOn
               joinQueryItem += sourceJoinOn
 
 
             // Generate join SQL for right side of through
             // Generate join SQL for right side of through
-            joinQueryItem += joinType + self.quoteTable(table, as) + " ON "
+            joinQueryItem += joinType + self.quoteTable( table, as ) + " ON "
               joinQueryItem += targetJoinOn
               joinQueryItem += targetJoinOn
 
 
 
 
-            if (include.where) {
+            if ( include.where ) {
               targetWhere = self.getWhereConditions(include.where, self.sequelize.literal(self.quoteIdentifier(as)), include.daoFactory, whereOptions)
               targetWhere = self.getWhereConditions(include.where, self.sequelize.literal(self.quoteIdentifier(as)), include.daoFactory, whereOptions)
               joinQueryItem += " AND "+ targetWhere
               joinQueryItem += " AND "+ targetWhere
               if (subQuery) {
               if (subQuery) {
                 if (!options.where) options.where = {}
                 if (!options.where) options.where = {}
 
 
                 // Creating the as-is where for the subQuery, checks that the required association exists
                 // Creating the as-is where for the subQuery, checks that the required association exists
-                var _where = "(";
-                  _where += "SELECT "+self.quoteIdentifier(identSource)+" FROM " + self.quoteTable(throughTable, throughAs);
-                  _where += joinType + self.quoteTable(table, as) + " ON "+targetJoinOn;
-                  _where += " WHERE " + sourceJoinOn + " AND " + targetWhere + " LIMIT 1"
-                _where += ")";
-                _where += " IS NOT NULL"
-
-                options.where["__"+throughAs] = self.sequelize.asIs(_where)
+                options.where["__"+throughAs] = self.sequelize.asIs([ '(',
+
+                	"SELECT " + self.quoteIdentifier( throughAs ) + "." + self.quoteIdentifier( identSource ) + " FROM " + self.quoteTable(throughTable, throughAs),
+									! include.required && joinType + self.quoteTable( association.source.tableName, tableSource ) + " ON " + sourceJoinOn || '',
+									joinType + self.quoteTable( table, as ) + " ON " + targetJoinOn,
+									"WHERE " + ( ! include.required && targetWhere || sourceJoinOn + " AND " + targetWhere ),
+									"LIMIT 1",
+
+                ')', 'IS NOT NULL'].join(' '))
               }
               }
             }
             }
           } else {
           } else {