Explain EXPLAIN PIPELINE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 5)
    ExpressionList (children 3)
     Identifier parent_key
     Identifier child_key
     Function count (children 1)
      ExpressionList
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier data_02233
    ExpressionList (children 2)
     Identifier parent_key
     Identifier child_key
    ExpressionList (children 2)
     OrderByElement (children 1)
      Identifier parent_key
     OrderByElement (children 1)
      Identifier child_key
    Set
