SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Literal NULL
    Literal \'\'
   TablesInSelectQuery (children 2)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (alias s1) (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 2)
          ExpressionList (children 2)
           Function toNullable (children 1)
            ExpressionList (children 1)
             Literal \'\'
           Literal NULL (alias key)
          ExpressionList (children 1)
           ExpressionList (children 1)
            Literal NULL
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      Subquery (alias s2) (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 2)
         SelectQuery (children 2)
          ExpressionList (children 2)
           Literal \'\' (alias key)
           Literal NULL (alias value)
          ExpressionList (children 1)
           ExpressionList (children 1)
            Literal \'\'
         SelectQuery (children 2)
          ExpressionList (children 2)
           Literal NULL (alias key)
           Function toNullable (alias value) (children 1)
            ExpressionList (children 1)
             Literal NULL
          ExpressionList (children 3)
           Literal \'\'
           Literal NULL
           Literal \'\'
     TableJoin (children 1)
      ExpressionList (children 1)
       Identifier key
