Explain EXPLAIN QUERY TREE (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Function mysql (children 1)
        ExpressionList (children 6)
         Literal \'127.0.0.1:9004\'
         Function currentDatabase (children 1)
          ExpressionList
         Identifier foo
         Literal \'default\'
         Literal \'\'
         Set
