SQL查詢與一個案件，當返回多個行

Question

我試圖做一個案件的查詢條件，看看我會顯示什麼列表，但我有這個錯誤ORA-01427: single-row subquery returns more than one row。

查詢是這樣的：

select 
CASE WHEN action_type like 'Trigger Severity' THEN (select cast(SEVERITY as varchar2(255)) name from SURV_TRIGGER_SEVERITY_LIST) 
    WHEN action_type like 'Host Group' then (select cast(name as varchar2(255)) name from Surv_List.groups) 
    WHEN action_type like 'Host' then (select cast(name as varchar2(255)) name from tn_tree) 
    END display_value 
from surv_action_type_list 
where id = 0 

是possibel調用查詢更多一行的情況下，條件裏面？

Answer 1

我會在多個步驟做到這一點。獲取操作類型，然後發出適當的查詢。無論你是在前端還是在存儲過程中都有這個邏輯，你就可能會依賴於很多其他的東西。

如果你絕對需要做這種方式，那麼你可以嘗試這樣的事：

SELECT 
    SQ.display_value 
FROM 
    surv_action_type_list SATL 
INNER JOIN 
    (
    SELECT 
     'Trigger Severity' action_type, 
     CAST(severity AS VARCHAR2(255)) display_value 
    FROM 
     SURV_TRIGGER_SEVERITY_LIST 
    UNION ALL 
    SELECT 
     'Host Group' action_type, 
     CAST(name AS VARCHAR2(255) display_value 
    FROM 
     Surv_List.groups 
    UNION ALL 
    SELECT 
     'Host' action_type, 
     CAST(name AS VARCHAR2(255) display_value 
    FROM 
     tn_tree 
    ) SQ ON 
    SQ.action_type = SATL.action_type 
WHERE 
    SATL.id = 0 

Answer 2

您有3個子查詢。

1. select cast(SEVERITY as varchar2(255)) name from SURV_TRIGGER_SEVERITY_LIST 
2. select cast(name as varchar2(255)) name from Surv_List.groups 
3. select cast(name as varchar2(255)) name from tn_tree 

每一個必須返回0或1行，但不是更多。

Answer 3

不可以。您的子查詢應該只返回一個值（只有一行和一列），因爲您將在單行中顯示它。

由於您使用上面的查詢將值顯示爲一列，所以您的意圖看起來像只有一個值。

select 
CASE WHEN action_type like 'Trigger Severity' THEN (select cast(SEVERITY as varchar2(255)) name from SURV_TRIGGER_SEVERITY_LIST) 
    WHEN action_type like 'Host Group' then (select cast(name as varchar2(255)) name from Surv_List.groups) 
    WHEN action_type like 'Host' then (select cast(name as varchar2(255)) name from tn_tree) 
    END display_value 
from surv_action_type_list 
where id = 0 

有沒有一個地方缺少的鏈接這個ID來說一個嚴重性列表？ 通常查詢這樣會在子查詢的條件..像..

select 
    CASE WHEN action_type like 'Trigger Severity' 
      THEN (select cast(SEVERITY as varchar2(255)) name 
         **from SURV_TRIGGER_SEVERITY_LIST trglst 
         where trglst.name = lst.severity_name** 
    ----- 
    --- 

     END display_value 
    from surv_action_type_list lst 
    where id = 0