Question

我正在尝试在嵌套中执行两个查询，但下面的查询没有给出任何o / p

select Object_name from IM_top where Id_number in
(select t.Id_number from IM_top t,IM_alarm_state a,IM_network_element n,Related_to_AH_id r
where t.Id_number = a.Id_number and t.Id_number = n.Id_number and t.Id_number *= r.Id_from
and t.Object_class like 'IM_top/IM_alarm_state/IM_network_element%') where Object_name not in (select substring(object,LEN(object)-CHARINDEX(',',REVERSE(object)) + 2,CHARINDEX(',',REVERSE(object)) + 1  ) from fmadb_1_1..FMA_alarm_text_route )

当我单独运行这些查询时，第一个查询返回2206行

select Object_name from IM_top where Id_number in
(select t.Id_number from IM_top t,IM_alarm_state a,IM_network_element n,Related_to_AH_id r
where t.Id_number = a.Id_number and t.Id_number = n.Id_number and t.Id_number *= r.Id_from
and t.Object_class like 'IM_top/IM_alarm_state/IM_network_element%')

，第二个查询返回184行

select substring(object,LEN(object)-CHARINDEX(',',REVERSE(object)) + 2,CHARINDEX(',',REVERSE(object)) + 1  ) from fmadb_1_1..FMA_alarm_text_route

我期待2206-184的差异，当我运行嵌套查询时它是2022行，但它给出的o / p是0行。

任何解决方法？

Answer 1

您的子查询返回NULL，这总是会产生一个空答案集：

a NOT IN（1，NULL）

在逻辑上等同于

a＆lt;＆gt; 1和a＆lt; 1＆gt; NULL

解析为

TRUE / FALSE AND UNKNOWN

最终导致

UNKNOWN

任何一行。

添加WHERE条件以删除NULL或更好地将NOT IN更改为NOT EXISTS。

Answer 2

您使用了两个Where条款而不是AND

试试这个

select Object_name from IM_top where Id_number in
(select t.Id_number from IM_top t,IM_alarm_state a,IM_network_element n,Related_to_AH_id r
where t.Id_number = a.Id_number and t.Id_number = n.Id_number and t.Id_number *= r.Id_from
and t.Object_class like 'IM_top/IM_alarm_state/IM_network_element%') AND Object_name not in (select substring(object,LEN(object)-CHARINDEX(',',REVERSE(object)) + 2,CHARINDEX(',',REVERSE(object)) + 1  ) from fmadb_1_1..FMA_alarm_text_route )

希望这能帮到你

嵌套查询未给出所需结果

2 个答案: