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these two tables are shown in Fig.
7
(a) and (b). In Q 6, in the SELECT clause two
physical columns
'
product_id
'
and
'
price
'
are speci
ed for the
'
product
'
CTT, and
two physical columns
'
sales_fact_id
'
and
'
unit_price
'
are speci
ed for the
'
sales_fact
'
CTT. In Q 7, in the SELECT clause two virtual columns are speci
ed.
The
rst column ID is 47, and the second column ID is 52 for the
'
product
'
VET
that equals 16. The column ID 47 corresponds to the
'
product_id
'
column, and the
column ID 52 corresponds to the
'
price
'
column of the
'
product
'
VET. In addi-
tion, in the SELECT clause two virtual columns are speci
ed for the
'
sales_fact
'
VET that equals 17. The
rst column is 55, and the second column is 61. The
column ID 55 corresponds to the
'
sales_fact_id
'
and the column ID 61 corre-
sponds to the
'
unit_price
'
of the
'
sales_fact
'
VET. Finally, in Q 8, in the SELECT
clause two physical columns
'
product_id
'
and
'
price
'
are speci
ed for the
'
rst column
is 55, and the second column is 61. The experimental results of Exp. 3 shows that
the query execution time of VET is faster than CTT, and CTT-and-VET is the
fastest of the three queries when 1 and 100 rows are retrieved. Moreover, this
experiment shows that the query execution times of the three types CTT, VET,
and CTT-and-VET are approximately the same when 1 row, and 100 rows are
retrieved. The details of the queries used in this experiment are shown in Tables
3
and
4
, the output of these queries is shown in Fig.
10
, and the throughputs of this
experiment are depicted in Fig.
16
(e) and (f).
product
'
CTT, and two virtual columns for the
'
sales_fact
'
VET. The
Fig. 10. The outputs of the Medium Query Experiment (Union)
(4) Medium-to-Complex Query Experiment
-
Left Join (Exp. 4): In this experi-
ment, the function of the Left Join Query Algorithm is invoked to use a left join
between three types of table combinations. First, two CTTs by executing Query 9
(Q 9) that comprises of IQ15
IQ17. The two CTTs are the
'
product
'
CTT and the
-
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