SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Identifier id
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier t1
   Function equals (children 1)
    ExpressionList (children 2)
     Function tuple (children 1)
      ExpressionList (children 2)
       Identifier s1
       Identifier s2
     Literal Tuple_(\'a\', \'b\')
