Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 2)
     Function plus (children 1)
      ExpressionList (children 2)
       Identifier b
       Literal UInt64_10
     Identifier a
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier column_swap_test_test
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier b
      Literal UInt64_0