code: function  getQueryTableSchema(tables, cb) {
  	var  tableSchema = {};
  
  	async.each(tables, function(t, callback) {
  		var  tbName = t.name;
  		schemaTool.getSchema(tbName, function(err, schema) {
  			if (!err)  {
  				tableSchema[tbName] = schema;
  				if (t.alias)
  					tableSchema[t.alias] = schema;
  			}
  			callback(err);
  		});
  	},
  	function(err) {
  		cb(err, tableSchema);
  	});
  }
docs: /*
  Retrieve all table schemas specified in a query.