不是单例函数

Question

tab1
ID_P , SYN
 1      0
 2      0
 2      1
 2      0

tab2
ID_P , SYN
 2      1
 2      1
 4      0

select CASE WHEN COUNT(SYN) > 1 THEN '0' 
            WHEN COUNT(SYN) = 0 AND SYN > 0 THEN '0' 
            ELSE '1' END 
from (
select COUNT(SYN) as SYN
from tab1
where ID_P = 2 and SYN <> '0' 
union
select COUNT(SYN) as SYN
from tab2
where ID_P = 2 and SYN <> '0' ) 

What i want to verify is

1. if the returned result from the unions have more than one row then return '0'
2. if the returned result from the unions just contain one row and the only result is bigger that zero then return '0'

The problem occurs int the second statement, ORA-00937 not a single-group group function , How can i overcome this problem ? The result should be zero because there are rows containing '1'. Thanks in advance Best regards

Answer 1

Actually m confused a bit by what actually you are trying to achieve, Below example might help you out

  SELECT
  CASE
    WHEN COUNT(1) > 1
    THEN '0'
    WHEN COUNT(1) =1
    AND MAX(A.SYN)     > 0
    THEN '0'
    ELSE '1'
  END col1
FROM
  (SELECT COUNT(SYN) AS SYN
  FROM
    (SELECT 1 ID_P,0 SYN FROM DUAL
    UNION ALL
    SELECT 2 ID_P,0 SYN FROM DUAL
    UNION ALL
    SELECT 2 ID_P,1 SYN FROM DUAL
    UNION ALL
    SELECT 2 ID_P,0 SYN FROM DUAL
    )
  WHERE ID_P = 2
  AND SYN   <> '0'
  UNION
  SELECT COUNT(SYN) AS SYN
  FROM
    (SELECT 2 ID_P,1 SYN FROM DUAL
    UNION ALL
    SELECT 2 ID_P,1 SYN FROM DUAL
    UNION ALL
    SELECT 4 ID_P,0 SYN FROM DUAL
    )
  WHERE ID_P = 2
  AND SYN   <> '0'
  ) a;