count函數應該返回0或空的，如果沒有行選擇

我已經寫了下面的查詢count函數應該返回0或空的，如果沒有行選擇

select process_status_count 
from (select count(*) as process_status_count from prod.process_status) 
where process_status_count <> 18;

要求：我想應該process_status_count則返回0狀態「process_status_count <> 18」不履行（process_status_count是18）。

但process_status_count沒有返回結果（也不爲空）。

請建議我需要做什麼更改，如果是process_status_count = 18，則結果爲零或爲空。

來源

2014-02-12 DJJ

計數可以在下面的查詢我使用和它工作正常返回0，但不能爲null – Miller

嘗試下面的查詢，

SELECT CASE process_status_count WHEN 18 THEN process_status_count ELSE 0 END 
FROM(
    SELECT COUNT(*) AS process_status_count 
    FROM prod.process_status 
    );

來源

2014-02-12 06:41:43 Dba

使用情況說明;

select case when process_status_count = 18 then 0 else process_status_count end from (select count(*) as process_status_count from sidewinder.process_status);

來源

2014-02-12 06:41:48 San

感謝你的努力:) – DJJ

= 18 then 0 else process_status_count end from（從sidewinder.process_status中選擇count（*）作爲process_status_count）; – DJJ

SQL> select count(*), decode(count(*), 18, count(*), 0) fullfill_cond 
    2 from user_objects 
    3/

    COUNT(*) FULLFILL_COND               
---------- -------------               
     937    0               

SQL> select count(*), decode(count(*), 937, count(*), 0) fullfill_cond 
    2 from user_objects 
    3/

    COUNT(*) FULLFILL_COND               
---------- -------------               
     937   937

來源

2014-02-12 06:43:53

希望這會幫助你：選擇情況下，當process_status_count：

with process_status 
as 
(
select 'Y' as process_status_count from dual 
connect by level <=18 
) 
select decode(count(process_status_count),18,0,count(process_status_count)) as status 
from process_status

來源

2014-02-12 07:19:44 narendra

count函數應該返回0或空的，如果沒有行選擇

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