ORA-00904 invalid identifier error in dynamic SQL block - oracle

Question

I'm running the below which once executed, an error is reported telling me that EST_ONE_ROW_MB is an invalid identifier.
I've been advised I perhaps need to get the dynamic SQL part running as a stand alone query to begin with as an initial troubleshooting exercise but I'm a bit stumped in terms of how to write a sub-query here that will produce the desired output and eliminate the error.
create or replace procedure JUST_ME is
--variables
l_dblink varchar2(100) := 'DB1';
file_handle UTL_FILE.file_type;
v_ts_name varchar2(30);
v_link_name varchar2(10);
v_csv_name varchar2(100);
EST_ONE_ROW_MB varchar2(100) ;
TOTAL_ROW_COUNT NUMBER;
SPACE_REQUIRED NUMBER;
TOT_OBJECT_SIZE_MB NUMBER;
v_Mv_name varchar2(100);
v_sql1 varchar2(1500);
cur SYS_REFCURSOR;
owner varchar2(100);
table_name varchar2(100);
driver_table varchar2(100);
mandatory_join varchar2(100);
C_TOTAL_ROW_COUNT varchar2(100);
v_total_driver_only varchar2(100);
--
begin
SELECT tablename into v_csv_name
FROM BOB01.BOB_new_table_tracker
WHERE
CREATED_AT = (select MAX(CREATED_AT) from BOB01.BOB_new_table_tracker);
SELECT mv_name into v_Mv_name
FROM BOB01.BOB_new_table_tracker_mv
WHERE
CREATED_AT = (select MAX(CREATED_AT) from BOB01.BOB_new_table_tracker_mv);
select link_name into v_link_name from link_and_mail where mdate = (select max(mdate) from link_and_mail);
select distinct targetschema into v_ts_name from BOB01.MV_BOB_TABLE;
v_sql1 := 'SELECT /*+ monitor parallel (4)*/ a.owner,
a.table_name,
b.driver_table,
b.mandatory_join,
sum(c.sum_bytes) TOT_OBJECT_SIZE_MB,
(TOT_OBJECT_SIZE_MB) / (:C_TOTAL_ROW_COUNT) AS "EST_ONE_ROW_MB",
(EST_ONE_ROW_MB) * (:TOTAL_ROW_COUNT) AS "SPACE_REQUIRED"
FROM dba_tables#DB1 a, '|| v_Mv_name ||' b, MV_PRD_SEG_DATA c
WHERE a.table_name IN ( SELECT table_name
FROM MV_BOB_TABLE
WHERE driver_table IS NOT NULL
AND additional_joins IS NULL
)
AND a.owner IN ( SELECT DISTINCT productionschema FROM MV_BOB_TABLE c )
and a.table_name = b.table_name
and a.table_name = c.segment_name
group by a.owner,a.table_name,b.driver_table,b.mandatory_join
ORDER BY table_name';
file_handle := utl_file.fopen('ESTIMATES_CSV', v_csv_name||'_EST_PROC.csv', 'w', 32767);
--
UTL_FILE.PUT_LINE(file_handle, ' ');
UTL_FILE.PUT_LINE(file_handle, 'The below report shows total row counts in PROD');
UTL_FILE.PUT_LINE(file_handle, ' for unjoined tables in the BOB document:');
UTL_FILE.PUT_LINE(file_handle, ' ');
utl_file.put_line(file_handle, 'OWNER,TABLE_NAME,MANDATORY_JOIN,TOT_OBJECT_SIZE_MB,EST_ONE_ROW_MB,TOTAL_ROW_COUNT,SPACE_REQUIRED');
--main loop
open cur for v_sql1 using TOTAL_ROW_COUNT,C_TOTAL_ROW_COUNT;
loop
fetch cur into OWNER,TABLE_NAME,MANDATORY_JOIN,TOT_OBJECT_SIZE_MB,EST_ONE_ROW_MB,TOTAL_ROW_COUNT,SPACE_REQUIRED;--,EST_ONE_ROW_MB;
exit when cur%NOTFOUND;
execute immediate' select /*+parallel (4)*/ count(*) from '||owner||'.'||table_name || '#' || l_dblink into TOTAL_ROW_COUNT;
execute immediate' select /*+monitor parallel (10)*/ count(*) from ' ||owner||'.'||table_name || '#' || l_dblink||' b '||','||
driver_table || '#' || l_dblink||' a ' ||' where ' ||mandatory_join into TOTAL_ROW_COUNT;
execute immediate' select /*+monitor parallel (10)*/ count(*) from ' ||owner||'.'||table_name || '#' || l_dblink into C_TOTAL_ROW_COUNT;
utl_file.put_line(file_handle,
OWNER || ',' ||
TABLE_NAME || ',' ||
TOT_OBJECT_SIZE_MB || ',' ||
TOTAL_ROW_COUNT || ',' ||
C_TOTAL_ROW_COUNT || ',' ||
round(TOT_OBJECT_SIZE_MB / C_TOTAL_ROW_COUNT,7)|| ',' ||
round(round(TOT_OBJECT_SIZE_MB / C_TOTAL_ROW_COUNT,7) * round(TOTAL_ROW_COUNT,0),0)
);
v_total_driver_only := v_total_driver_only + round(TOT_OBJECT_SIZE_MB / C_TOTAL_ROW_COUNT,7) * round(TOTAL_ROW_COUNT,0);
end loop;
UTL_FILE.PUT_LINE(file_handle, ' ');
utl_file.put_line(file_handle,
'Total Estimated Space Required '|| round(v_total_driver_only,0) ||' MB'
);
utl_file.fclose(file_handle);
end JUST_ME;

Answer 1

to use EST_ONE_ROW_MB on that way is not possible because its' not defied as column.
replace it by (TOT_OBJECT_SIZE_MB) / (:C_TOTAL_ROW_COUNT)
SELECT /*+ monitor parallel (4)*/ a.owner,
a.table_name,
b.driver_table,
b.mandatory_join,
sum(c.sum_bytes) TOT_OBJECT_SIZE_MB, -- will be the same problem
(sum(c.sum_bytes)) / (:C_TOTAL_ROW_COUNT) AS "EST_ONE_ROW_MB",
((sum(c.sum_bytes)) / (:C_TOTAL_ROW_COUNT)) * (:TOTAL_ROW_COUNT) AS "SPACE_REQUIRED"
...
you can do that if you have an Inline View. e.g.
select EST_ONE_ROW_MB * (:TOTAL_ROW_COUNT) AS "SPACE_REQUIRED"
from(
select (TOT_OBJECT_SIZE_MB) / (:C_TOTAL_ROW_COUNT) AS "EST_ONE_ROW_MB"
from ....
)