一、 查询要求
Q8语句是查询在过去的两年中一个给定零件类型在某国某地区市场份额的变化情况。
Q8语句的特点是：带有分组、排序、聚集、子查询操作并存的查询操作。子查询的父层查询不存在其他查询对象，是格式相对简单的子查询，但子查询自身是多表连接的查询。
二、 Oracle执行
Oracle编写的查询SQL语句如下：
select /*+ parallel(n) */
o_year,
sum(case
when nation = 'CHINA' then volume
else 0
end)/ sum(volume) as mkt_share
from
(
select
extract(year from o_orderdate) as o_year,
l_extendedprice * (1 - l_discount) as volume,
n2.n_name as nation
from
part,
supplier,
lineitem,
orders,
customer,
nation n1,
nation n2,
region
where
p_partkey = l_partkey
and s_suppkey = l_suppkey
and l_orderkey = o_orderkey
and o_custkey = c_custkey
and c_nationkey = n1.n_nationkey
and n1.n_regionkey = r_regionkey
and r_name = 'ASIA'
and s_nationkey = n2.n_nationkey
and o_orderdate between date '1995-01-01' and date '1996-12-31'
and p_type = 'STANDARD POLISHED BRASS'
) all_nations
group by
o_year
order by
o_year;
其中/*+ parallel(n) */ 是Oracle的并行查询语法，n是并行数。
脚本执行时间，单位：秒
并行数124812
Oracle472362277216192
三、 SPL优化
这里的orders与lineitem主子表关联优化原理与Q3中类似。
SPL脚本如下：
A
1=1
2=now()
3>nation="CHINA"
4>name="ASIA"
5>type="STANDARD POLISHED BRASS"
6=file(path+"region.ctx").create().cursor(R_REGIONKEY,R_NAME;R_NAME==name).fetch()
7=file(path+"nation.ctx").create().cursor(N_NATIONKEY,N_NAME,N_REGIONKEY).fetch()
8=A7.select(N_NAME==nation).derive@o().keys@i(N_NATIONKEY)
9=A7.switch@i(N_REGIONKEY, A6:R_REGIONKEY).keys@i(N_NATIONKEY)
101995-01-01
111996-12-31
12=file(path+"customer.ctx").create().cursor@m(C_CUSTKEY;A9.find(C_NATIONKEY);A1).fetch().keys@i(C_CUSTKEY)
13=file(path+"orders.ctx").create().cursor@m(O_ORDERKEY,O_ORDERDATE;O_ORDERDATE>=A10 && O_ORDERDATE <=A11 && A12.find(O_CUSTKEY);A1)
14=file(path+"supplier.ctx").create().cursor@m(S_SUPPKEY;A8.find(S_NATIONKEY);A1).fetch().keys@i(S_SUPPKEY)
15=file(path+"part.ctx").create().cursor@m(P_PARTKEY;P_TYPE==type;A1).fetch().keys@i(P_PARTKEY)
16=file(path+"lineitem.ctx").create().news(A13,L_ORDERKEY,L_SUPPKEY,L_EXTENDEDPRICE,L_DISCOUNT,O_ORDERDATE;A15.find(L_PARTKEY))
17=A16.switch(L_SUPPKEY,A14)
18=A16.new(O_ORDERDATE,L_EXTENDEDPRICE*(1-L_DISCOUNT):volume,if(L_SUPPKEY,volume,0):nvolume)
19=A18.groups( year(O_ORDERDATE):o_year;sum(nvolume):s1,sum(volume):s2)
20=A19.new(o_year,s1/s2:mkt_share)
21=now()
22=interval@s(A2,A21)
nation表作为外键表被用了两次，这里在A8,A9基于读出来的A7分别生成相应的外键表。
脚本执行时间，单位：秒
并行数 1 2 4 8 12
Oracle 472 362 277 216 192
SPL组表 315 162 92 46 37