Sql query taking forever to execute - sql

Question

Following is query that i am trying to execute and it is taking forever to execute.
SELECT DISTINCT (CLN_CLNDR_DT)FROM CLN_CLNDR CLN,
SYG_SYSTEM_GLOBALS SYG,CTD_CSH_TRNSCTN_DTLS CTD WHERE CLN.CLN_BP_ID = SYG.SYG_BP_ID AND CLN.CLN_ENTITY_ID = CTD.CTD_ENTITY_ID AND CLN_DT_SEQ_NUM
IN
(SELECT DISTINCT (CLN1.CLN_DT_SEQ_NUM)
FROM CLN_CLNDR CLN1,
SBD_SYS_BSNS_DTS SBD,
SYG_SYSTEM_GLOBALS SYG,
CTD_CSH_TRNSCTN_DTLS CTR
WHERE SBD.SBD_BSNS_DT = CLN1.CLN_CLNDR_DT
AND CLN1.OU_ID = SBD.OU_ID
AND CLN1.CLN_BP_ID = SYG.SYG_BP_ID
AND CLN1.CLN_ENTITY_ID = CTR.CTD_ENTITY_ID
);
When i try to run just the query inside in , it easily returns result as
(522,470,419,417,553,582,305,361)
SELECT DISTINCT (CLN1.CLN_DT_SEQ_NUM)
FROM CLN_CLNDR CLN1,
SBD_SYS_BSNS_DTS SBD,
SYG_SYSTEM_GLOBALS SYG,
CTD_CSH_TRNSCTN_DTLS CTR
WHERE SBD.SBD_BSNS_DT = CLN1.CLN_CLNDR_DT
AND CLN1.OU_ID = SBD.OU_ID
AND CLN1.CLN_BP_ID = SYG.SYG_BP_ID
AND CLN1.CLN_ENTITY_ID = CTR.CTD_ENTITY_ID;
Also when i try to execute directly the full query replacing the query inside in block
with the result of inner query that is (522,470,419,417,553,582,305,361),
It is working fine.
As i am new to this , i don't know what is going on .
Please help me with this.

Answer 1

I don't think you need all the tables in the subquery since you are already using them to filter rows in the outer query. Try this:
SELECT DISTINCT (CLN_CLNDR_DT)
FROM CLN_CLNDR CLN,
SYG_SYSTEM_GLOBALS SYG,
CTD_CSH_TRNSCTN_DTLS CTD
WHERE CLN.CLN_BP_ID = SYG.SYG_BP_ID
AND CLN.CLN_ENTITY_ID = CTD.CTD_ENTITY_ID
AND CLN_DT_SEQ_NUM
IN
(SELECT DISTINCT (CLN1.CLN_DT_SEQ_NUM)
FROM CLN_CLNDR CLN1,
SBD_SYS_BSNS_DTS SBD,
WHERE SBD.SBD_BSNS_DT = CLN1.CLN_CLNDR_DT
AND CLN1.OU_ID = SBD.OU_ID
);