SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 4)
   ExpressionList (children 2)
    Function concat (alias y) (children 1)
     ExpressionList (children 2)
      Literal \'t\'
      Identifier x
    Literal \'rue\' (alias x)
   ExpressionList (children 1)
    Asterisk
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 3)
          ExpressionList (children 1)
           Literal UInt64_1
          TablesInSelectQuery (children 1)
           TablesInSelectQueryElement (children 1)
            TableExpression (children 1)
             TableIdentifier tab
          Function equals (children 1)
           ExpressionList (children 2)
            Identifier y
            Literal \'true\'
   Set
