Inner join working too long

Question

First I am using Oracle 8i
The problem is next. I have two subqueries. Lets call them S1 and S2. Both have the field ID (which is of type varchar2(11) just from different tables T1 and T2).
S1 have about 8000 rows and S2 - 36000 (no problems here). We want to join these tables into one. It is simple? It should be. I wrote next query:
SELECT count(*)
FROM S1, S2
WHERE S1.ID = S2.ID
AND S1.date BETWEEN S2.from_date AND S.to_date
It is working. But it works very long. More than 30 min. I wrote another query with outer join.
SELECT count(*)
FROM S1, S2
WHERE S1.ID = S2.ID (+)
AND S1.date BETWEEN S2.from_date AND S.to_date
This one works less than one min. If i correctly understand - both queries should work for about the same amount of time. Could someone explain me what i am missing.

Answer 1

OK, here is my query. A.asm_ak and B.pacientas are fields of the same type and store the same data. First subquery give the list of the people and their visit dates from asm_nepatv and gydymo_lapai. Another subquery gives the list of the people and additional information from asmenys and other tables.
I checked these two tables asmenys and asm_nepatv. These fields do not have keys or indexes.
select count(*)
from
(select asm_ak, gal_atvykimo_data adata
from gydymo_lapai, asm_nepatv
where gal_asmn_id = asm_nepatv.asm_id
and asm_nepatv.asm_ak IS NOT NULL
and gal_pabaigos_data >= to_date(?,'YYYY.MM.DD')
and gal_pabaigos_data < to_date(?,'YYYY.MM.DD')
) A,   
select gist_pav, pas_profilis SPEC, asmenys.asm_ak pacientas, reg_data_nuo pnuo, reg_data_iki piki, asm.asm_pavarde||' '||asm.asm_vardas gdt, gdis_data_nuo gydnuo, gdis_data_iki gydiki
from asmenys, reg_gi, instaliacija, gyd_isidarbinimai, gydytojai, asmenys asm, gydymo_istaigos, darbo_vietos, paslaugos
where asmenys.asm_id = reg_gi.reg_asm_id
and reg_gi.reg_gist_id = instaliacija.gist_id
and reg_gi.reg_dv_id = gyd_isidarbinimai.gdis_dv_id
and dv_id = reg_dv_id
and dv_pas_id = pas_id
and gyd_isidarbinimai.gdis_gdt_id = gydytojai.gdt_id
and instaliacija.gist_id = gydymo_istaigos.gist_id
and gydytojai.gdt_asm_id = asm.asm_id
and reg_gi.reg_data_nuo <= to_date(?,'YYYY.MM.DD')
and reg_gi.reg_data_iki >= to_date(?,'YYYY.MM.DD')
and (to_date(?,'YYYY.MM.DD') - asmenys.asm_gim_data)/365.25 >= 0
and (to_date(?,'YYYY.MM.DD') - asmenys.asm_gim_data)/365.25 < 120
) B
where A.asm_ak = B.pacientas (+)
and A.adata between pnuo and pikiEdited by: user512088 on 2009.3.31 05.32
Edited by: user512088 on 2009.3.31 05.33
Edited by: user512088 on 2009.3.31 05.35
Edited by: user512088 on 2009.3.31 05.40