need SQL complex query help

SELECT * FROM (SELECT
mcat.CATALOG_ITEM_ID,
mcat.CATALOG_ITEM_NAME ,
mcat.DESCRIPTION,
mcat.CATALOG_ITEM_TYPE,
mcat.DELIVERY_METHOD,
XMLElement("TRAINING_PLAN",XMLAttributes( TP.TPLAN_ID as "id" ),
XMLELEMENT("COMPLETE_QUANTITY", TP.COMPLETE_QUANTITY),
XMLELEMENT("COMPLETE_UNIT", TP.COMPLETE_UNIT),
XMLElement("TOTAL_CREDITS", TP.numberOfCredits ),
XMLELEMENT("IS_CREDIT_BASED", TP.IS_CREDIT_BASED),
XMLELEMENT("IS_FOR_CERT", TP.IS_FOR_CERT),
XMLELEMENT("ACCREDIT_ORG_NAME", TP.ACCRED_ORG_NAME),
XMLELEMENT("ACCREDIT_ORG_ID", TP.accredit_org_id ),
XMLElement("OBJECTIVE_LIST", TP.OBJECTIVE_LIST )
).extract('/').getClobVal() AS PLAN_LIST

FROM
student_master_catalog mcat
INNER JOIN
(SELECT stu_tp.TPLAN_ID,
stu_tp.COMPLETE_QUANTITY,
stu_tp.COMPLETE_UNIT,
stu_tp.TPLAN_XML_DATA.extract('//numberOfCredits/text()').getStringVal() as numberOfCredits,
stu_tp.IS_CREDIT_BASED,
stu_tp.IS_FOR_CERT,
stu_oa.ACCRED_ORG_NAME,
stu_tp.TPLAN_XML_DATA.extract('//accreditingOrg/text()').getStringVal() as accredit_org_id,


objective_list.OBJECTIVE_LIST
FROM
student_training_catalog stu_tp
LEFT OUTER JOIN
stu_accrediting_org stu_oa on stu_tp.TPLAN_XML_DATA.extract('//accreditingOrg/text()').getStringVal() = stu_oa.ACCRED_ORG_ID
INNER JOIN
(SELECT *
FROM
(SELECT
stu_tpo.TPLAN_ID AS OBJECTIVE_TPLAN_ID,
XMLAgg(
XMLElement("OBJECTIVE",
XMLElement("OBJECTIVE_ID",stu_tpo.T_OBJECTIVE_ID ),
XMLElement("OBJECTIVE_NAME",stu_to.T_OBJECTIVE_NAME ),
XMLElement("OBJECTIVE_REQUIRED_CREDITS_OR_ACTIVITIES",stu_tpo.REQUIRED_CREDITS ),
XMLElement("ITEM_ORDER", stu_tpo.ITEM_ORDER ),
XMLElement("ACTIVITY_LIST", activity_list.ACTIVITY_LIST )
)
) as OBJECTIVE_LIST
FROM
stu_TP_OBJECTIVE stu_tpo
INNER JOIN
stu_TRAINING_OBJECTIVE stu_to ON stu_tpo.T_OBJECTIVE_ID = stu_to.T_OBJECTIVE_ID
INNER JOIN
(SELECT *
FROM
(SELECT stu_toa.T_OBJECTIVE_ID AS ACTIVITY_TOBJ_ID, XMLAgg(
XMLElement("ACTIVITY",
XMLElement("ACTIVITY_ID",stu_toa.ACTIVITY_ID ),
XMLElement("CATALOG_ID",COALESCE(stu_c.CATALOG_ID, COALESCE( stu_e.CATALOG_ID, stu_t.CATALOG_ID ) ) ),
XMLElement("CATALOG_ITEM_ID",COALESCE(stu_c.CATALOG_ITEM_ID, COALESCE( stu_e.CATALOG_ITEM_ID, stu_t.CATALOG_ITEM_ID ) ) ),
XMLElement("DELIVERY_METHOD",COALESCE(stu_c.DELIVERY_METHOD, COALESCE( stu_e.DELIVERY_METHOD, stu_t.DELIVERY_METHOD ) ) ),
XMLElement("ACTIVITY_NAME",COALESCE(stu_c.COURSE_NAME, COALESCE( stu_e.EVENT_NAME, stu_t.TEST_NAME ) ) ),
XMLElement("ACTIVITY_TYPE",initcap( stu_toa.ACTIVITY_TYPE ) ),
XMLElement("IS_REQUIRED",stu_toa.IS_REQUIRED ),
XMLElement("IS_PREFERRED",stu_toa.IS_PREFERRED ),
XMLElement("NUMBER_OF_CREDITS",stu_lac.CREDIT_HOURS),
XMLElement("ITEM_ORDER", stu_toa.ITEM_ORDER )
)) as ACTIVITY_LIST
FROM stu_TRAIN_OBJ_ACTIVITY stu_toa
LEFT OUTER JOIN
(
SELECT distinct lac.LEARNING_ACTIVITY_ID, lac.CREDIT_HOURS


FROM student_training_catalog tp
INNER JOIN stu_TP_OBJECTIVE tpo on tp.TPLAN_ID = tpo.TPLAN_ID
INNER JOIN stu_TRAIN_OBJ_ACTIVITY toa on tpo.T_OBJECTIVE_ID = toa.T_OBJECTIVE_ID
INNER JOIN stu_LEARNINGACTIVITY_CREDITS lac on lac.LEARNING_ACTIVITY_ID = toa.ACTIVITY_ID and tp.TPLAN_XML_DATA.extract ('//accreditingOrg/text()').getStringVal() = lac.ACC_ORG_ID
*where tp.tplan_id ='*************'*
) **stu_lac ON stu_lac.LEARNING_ACTIVITY_ID = stu_toa.ACTIVITY_ID ------>This Select returns correct no. of rows**

**I want to join the below nested SELECTS with stu_toa.ACTIVITY_ID.This would solve my issues

This below SELECT inside the LEFT OUTER JOIN is the Problem.it returns too much because 3 tables are joined directly without any value qualification**
LEFT OUTER JOIN
( SELECT ch.COURSE_HISTORY_ID, stu_c.COURSE_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method
FROM stu_COURSE stu_c
**LEFT OUTER JOIN stu_course_history ch on stu_c.course_id = ch.ch_course_id -
If i can qualify here with ch.ch_course_id = stu_toa.ACTIVITY_ID (stu_toa.ACTIVITY_ID from the above select with correct no. of rows )
Here,i get erros because i cant access outside values inside a left outer join**

LEFT OUTER JOIN student_master_catalog mca on ch.course_history_id = mca.catalog_item_id
) stu_c ON stu_c.COURSE_HISTORY_ID = stu_toa.ACTIVITY_ID

LEFT OUTER JOIN
(SELECT stu_e.EVENT_ID, stu_e.EVENT_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method FROM stu_EVENTS stu_e LEFT OUTER JOIN student_master_catalog mca on stu_e.event_Id = mca.catalog_item_id ) stu_e ON stu_e.EVENT_ID = stu_toa.ACTIVITY_ID
LEFT OUTER JOIN
(SELECT stu_t.TEST_HISTORY_ID, stu_t.TEST_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method FROM stu_TEST_HISTORY stu_t LEFT OUTER JOIN student_master_catalog mca on stu_t.test_history_id = mca.catalog_item_id) stu_t ON stu_t.test_history_id = stu_toa.ACTIVITY_ID
GROUP BY stu_toa.T_OBJECTIVE_ID) ) activity_list ON activity_list.ACTIVITY_TOBJ_ID = stu_tpo.T_OBJECTIVE_ID
GROUP BY stu_tpo.TPLAN_ID) ) objective_list ON objective_list.OBJECTIVE_TPLAN_ID = stu_tp.TPLAN_ID
)TP ON TP.TPLAN_ID = mcat.CATALOG_ITEM_ID
WHERE
mcat.CATALOG_ITEM_ID = '*****************' and mcat.CATALOG_ORG_ID = '********')

LEFT OUTER JOIN
     (  SELECT *

        FROM STUDENT_COURSE stu_c

        LEFT OUTER JOIN STUDENT_history ch on stu_c.course_id = ch.ch_course_id

        LEFT OUTER JOIN STUDENT_master stu_mca on ch.course_history_id = stu_mca.item_id

      ) stu_c ON stu_c.HISTORY_ID = toa.ACTIVITY_ID               ----->This table is joined earlier

LEFT OUTER JOIN

    (SELECT c_e.EV_ID, c_e.EV_NAME, ma.item_id, ma.cata_id