SQL/OLAP
Sang-Won Lee
Let’s e-Wha!
Email: swlee@ewha.ac.kr
URL: http://home.ewha.ac.kr/~swlee
Jul. 12th, 2001
SQL/OLAP
ISO/IEC JTC1 SC32
1
Contents
 Introduction to OLAP and SQL Issues
 Current OLAP Solutions
 SQL/OLAP
 Future OLAP Trends
SQL/OLAP
ISO/IEC JTC1 SC32
2
OLAP
 On-Line Analytical Processing
–
E.F. Codd coined the term “OLAP”([1])
–
Multi-dimensional data model
–
vs. On-Line Transaction Processing
–
vs. Data warehouse
SQL/OLAP
ISO/IEC JTC1 SC32
3
Multi-dimensional Data Model
 Sales(prod-id,store-id,time-id,qty,amt)
Dimension: Product, Store, Time
Hierarchy:
–
–
–
SQL/OLAP
Product -> Category -> Industry
Store->City -> State -> Country
Date -> Month -> Quarter -> Year
ISO/IEC JTC1 SC32
4
Multi-dimensional Data Model(2)
 Operations
–
–
–
–
–
–
–
roll-up/drill-down
slice/dice
pivot
ranking
comparisons
drill-across
etc.
 Example
–
–
–
for each state show me top 10 products based on total sales
what is the percentage growth of Jan-99 total sales
over total Jan-98?
for each product show me the quantity shipped and sold
SQL/OLAP
ISO/IEC JTC1 SC32
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OLAP Operations
 Many business operations was hard or impossible to
express in SQL
–
multiple aggregations
–
comparisons(with aggregation)
–
reporting features
 Be prepared for serious performance penalty
 Client and middle-ware tools provide the necessary
functionality
–
OLAP server: ROLAP vs. MOLAP
SQL/OLAP
ISO/IEC JTC1 SC32
6
Multiple Aggregations
 Create a 2-dimensional spreadsheets that shows sum
of sales by maker as well as model of car
 Each subtotal requires a separate aggregate query
Cross Tab
Chevy
Ford
By Color
RED
WHITE
BLUE
By Make
Sum
SQL/OLAP
SELECT color, make, sum(amt)
FROM sales
GROUP BY color, make
union
SELECT color, sum(amt)
FROM sales
GROUP BY color
union
SELECT make, sum(amt)
FROM sales
GROUP BY make
union
SELECT sum(amt)
FROM sales
ISO/IEC JTC1 SC32
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Comparisons
 Examples:
–
last year’s sales vs. this year’s sales for each product
 requires a self-join
VIEW:
create or replace view v_sales as
select prod-id, year, sum(qty) as sale_sum
from sales
group by prod-id, year;
QUERY:
select
cur.year cur_year,
cur.sale_cur_sales,
last.sum last_sales
from v_sales curr, v_sales last
where curr.year=(last.year+1)
SQL/OLAP
ISO/IEC JTC1 SC32
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The Data CUBE Relational Operator
Generalizes Group By and Aggregates
Aggregate
Group By
(with total)
Sum
By Color
RED
WHITE
BLUE
Cross Tab
Chevy Ford
Sum
By Color
RED
WHITE
BLUE
The Data Cube and
The Sub-Space Aggregates
By Make
Sum
By Year
By Make
By Make & Year
RED
WHITE
BLUE
By Color & Year
Sum
By Make & Color
By Color
source:[6]
SQL/OLAP
ISO/IEC JTC1 SC32
9
Getting Sub-totals: ROLLUP Operation
SELECT year, brand, SUM(qty)
FROM sales
GROUP BY ROLLUP (year, brand);
YEAR
1996
1996
1996
1996
1997
…
1997
SQL/OLAP
BRAND
Ford
Honda
Toyota
Ford
SUM(qty)
250
300
450
1000
300
1200
2200
ISO/IEC JTC1 SC32
Getting Cross-tabs: CUBE Operation
SELECT year, brand, SUM(amount)
FROM sales
GROUP BY CUBE (year, brand);
YEAR BRAND SUM(AMOUNT)
1996 Ford
250
...
1996 Toyota
450
1997 Ford
300
...
1997
1200
Ford
550
Honda
650
Toyota
1000
2200
SQL/OLAP
ISO/IEC JTC1 SC32
Flexible Grouping: GROUPING_SETS
Operator
SELECT year, brand, color, SUM(qty)
FROM sales
GROUP BY GROUPING_SETS ((year, brand),
(brand,color),());
YEAR BRAND
COLOR
1996 Ford
1996 Honda
1996 Toyota
1997 Ford
1997 Honda
1997 Toyota
Ford
Blue
Ford
Red
Honda
Blue
Toyota Red
Toyota White
SQL/OLAP
SUM(QTY)
250
300
450
300
350
550
400
150
650
700
300
2200
ISO/IEC JTC1 SC32
Year, Brand
Brand, Color
Grand total
LAG Operator
SQL> SELECT timekey, sales
2 LAG(sales, 12) OVER
3 (ORDER BY timekey) AS sales_last_year,
4 (sales - sales_last_year) AS sales_change
5 FROM sales;
TIMEKEY
98-1
…..
99-1
99-2
99-3
99-4
99-5
99-6
99-7
99-8
SQL/OLAP
SALES
1100
…
1200
1500
1700
1600
1800
1500
1300
1400
SALES_LAST_YEAR
…
1100
1450
1350
1700
1600
1450
1250
1200
ISO/IEC JTC1 SC32
SALES_CHANGE
...
100
50
250
-100
200
50
50
200
13
MOVING Average
SELECT time-id, avg(sum(qty))
over (order by time-id
RANGE INTERVAL ‘2’ DAY PRECEDING )
as mvg_avg_sales
from sales
group by time_id ;
SQL/OLAP
ISO/IEC JTC1 SC32
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