Explain EXPLAIN (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 2)
     Function divide (children 1)
      ExpressionList (children 2)
       Identifier x
       Literal UInt64_2
     Identifier y
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier tab
