Database Management System - SQL Advanced Training

Database Management System
Advanced Training
Practices in 2017
Prepared by: Moutasm Tamimi
Using SQL language
Microsoft SQL Server Management Studio
Versions (2008-2010-2012-2014)

Speaker Information
 Moutasm tamimi
Independent consultant , IT Researcher , CEO at ITG7
Instructor of: Project Development.
DBMS.
.NET applications.
Digital marketing.
Email: tamimi@itg7.com
LinkedIn: click here.

Joins
PName Price Category Manufacturer
Gizmo $19.99 Gadgets GizmoWorks
Powergizmo $29.99 Gadgets GizmoWorks
SingleTouch $149.99 Photography Canon
MultiTouch $203.99 Household Hitachi
Product
Company
Cname StockPrice Country
GizmoWorks 25 USA
Canon 65 Japan
Hitachi 15 Japan
PName Price
SingleTouch $149.99
SELECT PName, Price
FROM Product, Company
WHERE Manufacturer=CName AND Country=‘Japan’
AND Price <= 200

More Joins
Product (pname, price, category, manufacturer)
Company (cname, stockPrice, country)
Find all Chinese companies that manufacture products both in the
‘electronic’ and ‘toy’ categories
SELECT cname
FROM
WHERE

Cross Join
There are two tables A and B
A has a column Id and data (1,2,3)
B has a column Id and data (A,B)
If I put
Select A.Id, B.Id from A,B
This generates output as
A 1
B 1
C 1
A 2
B 2
C 2

Self Join
There is a table called Emp with the following structure:
empid ename mgrid
1 A null
2 B 1
3 C 1
4 D 2
If I want to print all managers using self join, I should write quey as:
select e1.ename from
emp e1,emp e2
where e1.mgrid = e2.empid

Inner Join
I have 2 tables Student(sid,Name) and Marks(Sid,Subject,Score)
If I want to print the marks of all students in the following format,
Name Subject Score
Select Name,Subject,Score from
Student s join Marks m
On s.sid = m.sid

Outer Join
 Right outer Join
 Print all the records in the second table with null values for missing records in the first
table
 Left outer Join
 Print all the records in the first table with null values for missing records in the second
table
 Full outer Join
 Prints all records in both the table with null values for missing records in both the table

Left Outer Join
I have a table Employee (Eid, Ename, Mid) and
a table Machine (Mid,ManufacturerName)
Employee
EidEName Mid
1 ABC1
2 DEF 3
Machine
Mid ManufacturerName
1 Zenith
2 HP

Left Outer Join
I want to print the employee name and machine name.
If I write a query using inner join, then the second employee will
not be displayed as the mid in his record is not avilable with the second
table.
So I go for left outer join. The query is as shown below:
Select Ename, ManufacturerName from Employee e left outer join
Machine m on e.Mid = m.Mid

Right outer Join
Assume data in the tables like this:
Employee
EidEName Mid
1 ABC1
2 DEF
Machine
1 Zenith
2 HP

Right Outer Join
If I want to find which machine is unallocated, I can use right outer join.
The query is as follows:
Select Ename, ManufacturerName from Employee e right outer join
This yields a result
ABCZenith
HP

Full Outer Join
Assume data in the tables like this:
Employee
EidEName Mid
1 ABC 1
2 DEF
3 GHI 2
Machine
1 Zenith
2 HP
3 Compaq

Full Outer Join
If I want to find people who have been un allocated with a system and
machines that are been un allocated, I can go for full outer join.
Query is like this:
Select Ename, ManufacturerName from Employee e full outer join
This yields a result
ABC Zenith
DEF
GHIHP
Compaq

Tuple Variables
SELECT DISTINCT pname, address
FROM Person, Company
WHERE worksfor = cname
Which
address ?
Person(pname, address, worksfor)
Company(cname, address)
SELECT DISTINCT Person.pname, Company.address
FROM Person, Company
WHERE Person.worksfor = Company.cname
SELECT DISTINCT x.pname, y.address
FROM Person AS x, Company AS y
WHERE x.worksfor = y.cname

SQL Functions
 SQL Avg()
 SQL Count()
 SQL First()
 SQL Last()
 SQL Max()
 SQL Min()
 SQL Sum()
 SQL Group By
• SQL HavingSQL Ucase()
• SQL Lcase()
• SQL Mid()
• SQL Len()
• SQL Round()
• SQL Now()
• SQL Format()

Aggregation
SELECT count(*)
FROM Product
WHERE year > 1995
Except count, all aggregations apply to a single attribute
SELECT avg(price)
FROM Product
WHERE maker=“Toyota”
SQL supports several aggregation operations:
sum, count, min, max, avg

COUNT applies to duplicates, unless otherwise stated:
SELECT Count(category)
FROM Product
WHERE year > 1995
same as Count(*)
We probably want:
SELECT Count(DISTINCT category)
FROM Product
WHERE year > 1995
Aggregation: Count

Purchase(product, date, price, quantity)
More Examples
SELECT Sum(price * quantity)
FROM Purchase
FROM Purchase
WHERE product = ‘bagel’
What do
they mean ?

Simple Aggregations
Purchase
Product Date Price Quantity
Bagel 10/21 1 20
Banana 10/3 0.5 10
Banana 10/10 1 10
Bagel 10/25 1.50 20
FROM Purchase
WHERE product = ‘bagel’
50 (= 20+30)

Grouping and Aggregation
Purchase(product, date, price, quantity)
SELECT product, Sum(price*quantity) AS TotalSales
FROM Purchase
WHERE date > ‘10/1/2005’
GROUP BY product
Let’s see what this means…
Find total sales after 10/1/2005 per product.

Grouping and Aggregation
1. Compute the FROM and WHERE clauses.
2. Group by the attributes in the GROUPBY
3. Compute the SELECT clause: grouped attributes and aggregates.

1&2. FROM-WHERE-GROUPBY
Bagel 10/21 1 20
Bagel 10/25 1.50 20
Banana 10/3 0.5 10
Banana 10/10 1 10

3. SELECT
FROM Purchase
WHERE date > ‘10/1/2005’
GROUP BY product
Bagel 10/21 1 20
Bagel 10/25 1.50 20
Banana 10/3 0.5 10
Banana 10/10 1 10
Product TotalSales
Bagel 50
Banana 15

GROUP BY v.s. Nested Quereis
FROM Purchase
WHERE date > ‘10/1/2005’
GROUP BY product
SELECT DISTINCT x.product, (SELECT Sum(y.price*y.quantity)
FROM Purchase y
WHERE x.product = y.product
AND y.date > ‘10/1/2005’)
AS TotalSales
FROM Purchase x
WHERE x.date > ‘10/1/2005’

Another Example
SELECT product,
sum(price * quantity) AS SumSales
max(quantity) AS MaxQuantity
FROM Purchase
GROUP BY product
What does
it mean ?

HAVING Clause
SELECT product, Sum(price * quantity)
FROM Purchase
WHERE date > ‘10/1/2005’
GROUP BY product
HAVING Sum(quantity) > 30
Same query, except that we consider only products that had
at least 100 buyers.
HAVING clause contains conditions on aggregates.

General form of Grouping and
Aggregation
SELECT S
FROM R1,…,Rn
WHERE C1
GROUP BY a1,…,ak
HAVING C2
S = may contain attributes a1,…,ak and/or any aggregates but NO OTHER
ATTRIBUTES
C1 = is any condition on the attributes in R1,…,Rn
C2 = is any condition on aggregate expressions
Why ?

General form of Grouping and Aggregation
Evaluation steps:
1. Evaluate FROM-WHERE, apply condition C1
2. Group by the attributes a1,…,ak
3. Apply condition C2 to each group (may have aggregates)
4. Compute aggregates in S and return the result
SELECT S
FROM R1,…,Rn
WHERE C1
GROUP BY a1,…,ak
HAVING C2

Advanced SQLizing
1. Getting around INTERSECT and EXCEPT
2. Quantifiers
3. Aggregation v.s. subqueries

1. INTERSECT and EXCEPT:
(SELECT R.A, R.B
FROM R)
INTERSECT
(SELECT S.A, S.B
FROM S)
SELECT R.A, R.B
FROM R
WHERE
EXISTS(SELECT *
FROM S
WHERE R.A=S.A and R.B=S.B)
(SELECT R.A, R.B
FROM R)
EXCEPT
(SELECT S.A, S.B
FROM S)
SELECT R.A, R.B
FROM R
WHERE
NOT EXISTS(SELECT *
FROM S
WHERE R.A=S.A and R.B=S.B)
If R, S have no
duplicates, then can
write without
subqueries
(HOW ?)
INTERSECT and EXCEPT: not in SQL Server

2. Quantifiers
Product ( pname, price, company)
Company( cname, city)
Find all companies that make some products with price < 100
SELECT DISTINCT Company.cname
FROM Company, Product
WHERE Company.cname = Product.company and Product.price < 100
Existential: easy ! 

2. Quantifiers
Product ( pname, price, company)
Company( cname, city)
Find all companies s.t. all of their products have price < 100
Universal: hard ! 
Find all companies that make only products with price < 100
same as:

2. Quantifiers
2. Find all companies s.t. all their products have price < 100
1. Find the other companies: i.e. s.t. some product  100
FROM Company
WHERE Company.cname IN (SELECT Product.company
FROM Product
WHERE Produc.price >= 100
FROM Company
WHERE Company.cname NOT IN (SELECT Product.company
FROM Product
WHERE Produc.price >= 100

3. Group-by v.s. Nested Query
 Find authors who wrote  10 documents:
 Attempt 1: with nested queries
SELECT DISTINCT Author.name
FROM Author
WHERE count(SELECT Wrote.url
FROM Wrote
WHERE Author.login=Wrote.login)
> 10
This is
SQL by
a novice
Author(login,name)
Wrote(login,url)

 Find all authors who wrote at least 10 documents:
 Attempt 2: SQL style (with GROUP BY)
SELECT Author.name
FROM Author, Wrote
WHERE Author.login=Wrote.login
GROUP BY Author.name
HAVING count(wrote.url) > 10
This is
SQL by
an expert
No need for DISTINCT: automatically from GROUP BY

Find authors with vocabulary  10000 words:
SELECT Author.name
FROM Author, Wrote, Mentions
WHERE Author.login=Wrote.login AND Wrote.url=Mentions.url
GROUP BY Author.name
HAVING count(distinct Mentions.word) > 10000
Author(login,name)
Wrote(login,url)
Mentions(url,word)

Two Examples
Store(sid, sname)
Product(pid, pname, price, sid)
Find all stores that sell only products with price > 100
same as:
Find all stores s.t. all their products have price > 100)

SELECT Store.name
FROM Store, Product
WHERE Store.sid = Product.sid
GROUP BY Store.sid, Store.name
HAVING 100 < min(Product.price)
SELECT Store.name
FROM Store
WHERE Store.sid NOT IN
(SELECT Product.sid
FROM Product
WHERE Product.price <= 100)
SELECT Store.name
FROM Store
WHERE
100 < ALL (SELECT Product.price
FROM product
WHERE Store.sid = Product.sid)
Almost equivalent…
Why both ?

Two Examples
Store(sid, sname)
Product(pid, pname, price, sid)
For each store,
find its most expensive product

Two Examples
SELECT Store.sname, max(Product.price)
FROM Store, Product
WHERE Store.sid = Product.sid
GROUP BY Store.sid, Store.sname
SELECT Store.sname, x.pname
FROM Store, Product x
WHERE Store.sid = x.sid and
x.price >=
ALL (SELECT y.price
FROM Product y
WHERE Store.sid = y.sid)
This is easy but doesn’t do what we want:
Better:
But may
return
multiple
product names
per store

Two Examples
SELECT Store.sname, max(x.pname)
FROM Store, Product x
WHERE Store.sid = x.sid and
x.price >=
ALL (SELECT y.price
FROM Product y
WHERE Store.sid = y.sid)
GROUP BY Store.sname
Finally, choose some pid arbitrarily, if there are many
with highest price:

NULLS in SQL
 Whenever we don’t have a value, we can put a NULL
 Can mean many things:
 Value does not exists
 Value exists but is unknown
 Value not applicable
 Etc.
 The schema specifies for each attribute if can be null (nullable
attribute) or not
 How does SQL cope with tables that have NULLs ?

Null Values
 If x= NULL then 4*(3-x)/7 is still NULL
 If x= NULL then x=“Joe” is UNKNOWN
 In SQL there are three boolean values:
FALSE = 0
UNKNOWN = 0.5
TRUE = 1

Null Values
 C1 AND C2 = min(C1, C2)
 C1 OR C2 = max(C1, C2)
 NOT C1 = 1 – C1
Rule in SQL: include only tuples that yield TRUE
SELECT *
FROM Person
WHERE (age < 25) AND
(height > 6 OR weight > 190)
E.g.
age=20
heigth=NULL
weight=200

Null Values
Unexpected behavior:
Some Persons are not included !
SELECT *
FROM Person
WHERE age < 25 OR age >= 25

Null Values
Can test for NULL explicitly:
 x IS NULL
 x IS NOT NULL
Now it includes all Persons
SELECT *
FROM Person
WHERE age < 25 OR age >= 25 OR age IS NULL

Outerjoins
Explicit joins in SQL = “inner joins”:
Product(name, category)
Purchase(prodName, store)
SELECT Product.name, Purchase.store
FROM Product JOIN Purchase ON
Product.name = Purchase.prodName
FROM Product, Purchase
WHERE Product.name = Purchase.prodName
Same as:
But Products that never sold will be lost !

Outerjoins
Left outer joins in SQL:
Purchase(prodName, store)
FROM Product LEFT OUTER JOIN Purchase ON

Name Category
Gizmo gadget
Camera Photo
OneClick Photo
ProdName Store
Gizmo Wiz
Camera Ritz
Camera Wiz
Name Store
Gizmo Wiz
Camera Ritz
Camera Wiz
OneClick NULL
Product Purchase

Application
Compute, for each product, the total number of sales in
‘September’
Purchase(prodName, month, store)
SELECT Product.name, count(*)
FROM Product, Purchase
WHERE Product.name = Purchase.prodName
and Purchase.month = ‘September’
GROUP BY Product.name
What’s wrong ?

Application
Compute, for each product, the total number of sales in
‘September’
Purchase(prodName, month, store)
SELECT Product.name, count(*)
FROM Product LEFT OUTER JOIN Purchase ON
and Purchase.month = ‘September’
GROUP BY Product.name
Now we also get the products who sold in 0 quantity

Outer Joins
 Left outer join:
 Include the left tuple even if there’s no match
 Right outer join:
 Include the right tuple even if there’s no match
 Full outer join:
 Include the both left and right tuples even if there’s no match

Modifying the Database
Three kinds of modifications
 Insertions
 Deletions
 Updates
Sometimes they are all called “updates”

Insertions
General form:
Missing attribute  NULL.
May drop attribute names if give them in order.
INSERT INTO R(A1,…., An) VALUES (v1,…., vn)
INSERT INTO Purchase(buyer, seller, product, store)
VALUES (‘Joe’, ‘Fred’, ‘wakeup-clock-espresso-machine’,
‘The Sharper Image’)
Example: Insert a new purchase to the database:

Insertions
INSERT INTO PRODUCT(name)
SELECT DISTINCT Purchase.product
FROM Purchase
WHERE Purchase.date > “10/26/01”
The query replaces the VALUES keyword.
Here we insert many tuples into PRODUCT

Insertion: an Example
prodName is foreign key in Product.name
Suppose database got corrupted and we need to fix it:
name listPrice category
gizmo 100 gadgets
prodName buyerName price
camera John 200
gizmo Smith 80
camera Smith 225
Task: insert in Product all prodNames from Purchase
Product
Product(name, listPrice, category)
Purchase(prodName, buyerName, price)
Purchase

INSERT INTO Product(name)
SELECT DISTINCT prodName
FROM Purchase
WHERE prodName NOT IN (SELECT name FROM Product)
gizmo 100 Gadgets
camera - -

INSERT INTO Product(name, listPrice)
SELECT DISTINCT prodName, price
FROM Purchase
WHERE prodName NOT IN (SELECT name FROM Product)
gizmo 100 Gadgets
camera 200 -
camera ?? 225 ?? -
Depends on the implementation

Deletions
DELETE FROM PURCHASE
WHERE seller = ‘Joe’ AND
product = ‘Brooklyn Bridge’
Factoid about SQL: there is no way to delete only a single
occurrence of a tuple that appears twice
in a relation.
Example:

Updates
UPDATE PRODUCT
SET price = price/2
WHERE Product.name IN
(SELECT product
FROM Purchase
WHERE Date =‘Oct, 25, 1999’);
Example:

Database Management System - SQL Advanced Training

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