Creating two distinct columns using WHERE clause from the same main table - oracle-sqldeveloper

Question

I need to pull two columns (B and C) from the same column (A) from Table_2. These two columns (script below) are implemented into a larger query. When I run the query with only one of the columns, for instance only B, then the query runs well and in just a few seconds. However, when I run both B and C within the query at the same time, the query just keeps running and does not end. I have tried giving the two columns different aliases to see if that would solve the problem, but I have not been able to figure out why the query does not run with both B and C present. The two columns are almost the same apart from the WHERE clause.
I only have one join in the script for both B and C columns similar to: FROM Table_1 T1, Table_2 T2 WHERE T2.ENT_REF = T1.ENT_REF (+)
Any ideas?
( SELECT
SUM(T2.A) as prem
FROM Table_2 T2
WHERE T2.ENT_REF = T1.ENT_REF
AND UPPER(T2.PER) = 'HURR'
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) B,
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2
WHERE T2.ENT_REFE = T1.ENT_REF
AND UPPER(T2.PER) IN ('I', 'II', 'II')
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) C

Answer 1

You need the dummy table in PL/SQL. (From dual)
You also need to join the table (table_1).
Please make sure that every single query can return your expected value.
In your original queries, you put 'T2.ENT_REF = T1.ENT_REF' but you did not add the table_1. This will cause the syntax error.
Please try this:
SELECT
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REF = T1.ENT_REF
AND UPPER(T2.PER) = 'HURR'
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) as B,
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REFE = T1.ENT_REF
AND UPPER(T2.PER) IN ('I', 'II', 'II')
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) as C
FROM DUAL
Update:
You can use [concat]
SELECT
CONCAT(
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REF = T1.ENT_REF
AND UPPER(T2.PER) = 'HURR'
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) ,
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REFE = T1.ENT_REF
AND UPPER(T2.PER) IN ('I', 'II', 'II')
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
)
) AS BandC
FROM DUAL
Update 2:
SELECT
(
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REF = T1.ENT_REF
AND UPPER(T2.PER) = 'HURR'
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
) +
(SELECT
SUM(T2.A) as prem
FROM Table_2 T2, Table_2 T1
WHERE T2.ENT_REFE = T1.ENT_REF
AND UPPER(T2.PER) IN ('I', 'II', 'II')
AND UPPER(T2.ENT_TYPE) = 'POL'
AND T2.Cov NOT IN ('OUTPROP','COV')
)
) AS BandC
FROM DUAL