Counting rows based on a column value

Question

Tricky Query.No offence if this is a repeat please.
This is a PROD issue in SYBASE.
TableA has id_flag_listing column
TableA
id_flag_listing
N
N
N
N
N
1) If all rows are set to 'N',then my count should be 0.
   PrimaryListing
   0
2) If there is one row which is 'Y' then this shoud be:
   id_flag_listing
   N
   N
   Y
   N
   N
   PrimaryListing
   1
How can I count in this manner?
Do i use decode? I am using
Select sum(decode(flg_active),'Y',1,0))
from TABLEA
Will the above work.??
I am using SQL for Sybase.
Please guide?

Answer 1

Did you even tried the SQL query I've given?
Your table A
SQL> SELECT flg_listing
  2  FROM
  3  (
  4     SELECT 'N' flg_listing FROM DUAL
  5     UNION ALL
  6     SELECT 'N' FROM DUAL
  7     UNION ALL
  8     SELECT 'N' FROM DUAL
  9     UNION ALL
10     SELECT 'N' FROM DUAL
11     UNION ALL
12     SELECT 'N' FROM DUAL
13  ) TABLEA;
FLG_LISTING
N
N
N
N
N
Your table A, from which I count where are of 'Y' value. In these queries, I change TableA contents.
SQL> SELECT count(*)
  2  FROM
  3  (
  4     SELECT 'N' flg_listing FROM DUAL
  5     UNION ALL
  6     SELECT 'N' FROM DUAL
  7     UNION ALL
  8     SELECT 'N' FROM DUAL
  9     UNION ALL
10     SELECT 'N' FROM DUAL
11     UNION ALL
12     SELECT 'N' FROM DUAL
13  ) TABLEA
14  WHERE flg_listing = 'Y';
  COUNT(*)
         0
SQL> SELECT count(*)
  2  FROM
  3  (
  4     SELECT 'N' flg_listing FROM DUAL
  5     UNION ALL
  6     SELECT 'N' FROM DUAL
  7     UNION ALL
  8     SELECT 'Y' FROM DUAL
  9     UNION ALL
10     SELECT 'N' FROM DUAL
11     UNION ALL
12     SELECT 'N' FROM DUAL
13  ) TABLEA
14  WHERE flg_listing = 'Y';
  COUNT(*)
         1
SQL> SELECT count(*)
  2  FROM
  3  (
  4     SELECT 'N' flg_listing FROM DUAL
  5     UNION ALL
  6     SELECT 'N' FROM DUAL
  7     UNION ALL
  8     SELECT 'Y' FROM DUAL
  9     UNION ALL
10     SELECT 'Y' FROM DUAL
11     UNION ALL
12     SELECT 'Y' FROM DUAL
13  ) TABLEA
14  WHERE flg_listing = 'Y';
  COUNT(*)
         3Yoann.