SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 3)
    Identifier a
    Function xxHash32 (children 1)
     ExpressionList (children 1)
      Identifier a
    Function xxHash32 (children 1)
     ExpressionList (children 1)
      Function tuple (children 1)
       ExpressionList (children 1)
        Identifier a
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier test_mix_null
