Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 3)
     Function plus (children 1)
      ExpressionList (children 2)
       Identifier x3
       Literal UInt64_1
     Identifier x2
     Identifier x1
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier test
    ExpressionList (children 1)
     OrderByElement (children 1)
      Literal UInt64_1