Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Function uniq (children 1)
      ExpressionList (children 1)
       Function concatAssumeInjective (children 1)
        ExpressionList (children 2)
         Literal \'x\'
         Literal \'y\'
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Function numbers (children 1)
        ExpressionList (children 1)
         Literal UInt64_10
