How to get count of a column value returned using subquery? - sql

Question

I want to get all hrc_acct_num which are not present in acct_key column of STAGING_CUST_ACCT table. The last outer select column is throwing an error. How can I get count of a column returned using a subquery?
SELECT source_sys_cd,
Count(CASE
WHEN is_delete = 0 THEN 1
END) [DEL IS 0],
Sum(CASE
WHEN trans_amt = 0 THEN 1
ELSE 0
END) [STG $0 TXN CNT],
Count(CASE
WHEN hrc_acct_num NOT IN(SELECT DISTINCT acct_key
FROM staging_cust_acct) THEN
hrc_acct_num
END)
FROM staging_transactions (nolock)
GROUP BY source_sys_cd
ORDER BY source_sys_cd

Answer 1

You can do a LEFT JOIN to the sub query and then do a SUM when the value is null. acct_key
SELECT source_sys_cd,
Count(CASE
WHEN is_delete = 0 THEN 1
END) [DEL IS 0],
Sum(CASE
WHEN trans_amt = 0 THEN 1
ELSE 0
END) [STG $0 TXN CNT],
SUM(CASE WHEN T.acct_key is NULL THEN 1 else 0 END ) CountNotIN
FROM staging_transactions (nolock) s
LEFT JOIN (SELECT DISTINCT acct_key
FROM staging_cust_acct) t
s.hrc_acct_num = t.acct_key
GROUP BY source_sys_cd
ORDER BY source_sys_cd
Here's a simplified demo

Answer 2

You can short circuit the subquery with NOT EXISTS. It's more efficient than LEFT JOIN (SELECT DISTINCT, since you don't care about enumerating all the times it does exist.
SELECT source_sys_cd,
Count(CASE is_delete WHEN
WHEN is_delete = 0 THEN 1
END) [DEL IS 0],
Count(CASE
WHEN trans_amt = 0 THEN 1
END) [STG $0 TXN CNT],
Count(CASE
WHEN NOT EXISTS (SELECT 1
FROM staging_cust_acct
WHERE acct_key = hrc_acct_num) THEN 1
END)
FROM staging_transactions (nolock)
GROUP BY source_sys_cd
ORDER BY source_sys_cd