1. Programming with Android:
Data management
Dr. ASM M Rahaman

2. Managing Data Preferences: Key/Value pairs of data
Direct File I/O: Read/write files onboard or on SD cards. Remember to request permission for writing, for instance, on SD card
Database Tables: SQL Lite
Application Direct Access: Read only access from res assets/raw directories
Increase functionality:
Content Providers: expose data to other applications
Services: background processes that run detached from any view

3. SQLite General purpose solution Standard SQL syntax
– Lightweight database based on SQL
Standard SQL syntax
SELECT name FROM table WHERE name = “Luca”
Android gives a standard interface to SQL tables of other apps For application tables no content providers are needed

4. Better to use constants like
 A database to store information
 Useful for structured informations
 Create a DBHelper which extends SQLiteOpenHelper
 Fill it with methods for managing the database
Better to use constants like
TABLE_GRADES
COLUMN_NAME
• ….

5.  Our database will look like this:
SQLite: example
 Our database will look like this:
 grade table:
 id: integer, primary key, auto increment
 firstName: text, not null
 lastName: text, not null
 class: text, not null
 grade: integer, not null

6. SQLite: better to use constants
 Useful for query definition
 Our constants?
private static final String DB_NAME = “grades.db”;; private static final int DB_VERSION = 1;;
public static final String TABLE_GRADES = “grades”;; public static final String COL_ID = “id”;;
public static final String COL_FIRSTNAME = “firstName”;; public static final String COL_LASTNAME = “lastName”;; public static final String COL_CLASS = “class”;;
public static final String COL_GRADE = “grade”;;

7.  Constructor: call the superconstructor
SQLite: creation code
 Constructor: call the superconstructor
Public mySQLiteHelper(Context context) { super(context, DB_NAME, null, DB_VERSION);; }
 onCreate(SQLiteDatabase db): create the tables
String sql_grade = “create table “ + TABLE_GRADES + “( “ + COL_ID + “ integer primary key autoincrement, “ + COL_FIRSTNAME + “ text not null, “ + COL_LASTNAME + “ text not null, “ +
COL_CLASS + “ text not null, “ + COL_GRADE + “ text not null “);;”;;
db.execSQL(sql_grade);;

8.  Create a public method, like insertDb(…)
SQLite: insert code
 Create a public method, like insertDb(…)
mySQLiteHelper sql = new mySQLiteHelper(InsertActivity.this);; SQLiteDatabase db = mySQLiteHelper.getWritableDatabase();; ContentValues cv = new ContentValues();; cv.put(mySQLiteHelper.COL_FIRSTNAME, firstName);; cv.put(mySQLiteHelper.COL_LASTNAME, lastName);; cv.put(mySQLiteHelper.COL_CLASS, className);; cv.put(mySQLiteHelper.COL_GRADE, grade);;
long id = db.insert(mySQLiteHelper.TABLE_GRADES, null, values);;

9.  Create a public method, like deleteDb(…)
SQLite: delete code
 Create a public method, like deleteDb(…)
 The delete method returns the number of rows affected
 Example:
db.delete(mySQLiteHelper.TABLE_GRADES, “id = ?”, new String[]
{Integer.toString(id_to_delete)});;

10.  Create a public method, like updateDb(…)
SQLite: update code
 Create a public method, like updateDb(…)
ContentValues cv = new ContentValues();; values.put(mySQLiteHelper.FIRSTNAME, firstName);; values.put(mySQLiteHelper.LASTNAME, lastName);;
db.update(mySQLiteHelper.TABLE_GRADES, values, “id = ?”, new
{Integer.toString(id_to_update));;
String[]

11.  Create a public method, like getFromDb(…)
SQLite: search code
 Create a public method, like getFromDb(…)
Cursor gradeCursor = db.query(mySQLiteHelper.TABLE_GRADES,
new String[]{mySQLiteHelper.COL_GRADE}, mySQLiteHelper.COL_ID + “ = “
+ id_to_search_for, null, null, null, null);;

12. SQL Data Definition Language (DDL) Data Manipulation Language (DML)
Create/alter/delete tables and their attributes
Following lectures...
Data Manipulation Language (DML)
Query one or more tables – discussed next !
Insert/delete/modify tuples in tables

13. PName Price Category Manufacturer Gizmo $19.99 Gadgets GizmoWorks
Tables in SQL
Table name
Attribute names
Product
PName
Price
Category
Manufacturer
Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
Tuples or rows

14. Tables Explained
The schema of a table is the table name and its attributes:
Product(PName, Price, Category, Manfacturer)
A key is an attribute whose values are unique; we underline a key

15. Data Types in SQL Atomic types: Characters: CHAR(20), VARCHAR(50)
Numbers: INT, BIGINT, SMALLINT, FLOAT
Others: MONEY, DATETIME, …

16. Data Definition Language
The SQL data-definition language (DDL) allows the specification of information about relations, including:
The schema for each relation.
The domain of values associated with each attribute.
Integrity constraints
And as we will see later, also other information such as
The set of indices to be maintained for each relations.
Security and authorization information for each relation.
The physical storage structure of each relation on disk.

17. Domain Types in SQL
char(n). Fixed length character string, with user-specified length n.
varchar(n). Variable length character strings, with user-specified maximum length n.
int. Integer (a finite subset of the integers that is machine-dependent).
smallint. Small integer (a machine-dependent subset of the integer domain type).
numeric(p,d). Fixed point number, with user-specified precision of p digits, with d digits to the right of decimal point. (ex., numeric(3,1), allows 44.5 to be stores exactly, but not or 0.32)
real, double precision. Floating point and double-precision floating point numbers, with machine-dependent precision.
float(n). Floating point number, with user-specified precision of at least n digits.
More are covered in Chapter 4.

18. Create Table Construct
An SQL relation is defined using the create table command:
create table r (A1 D1, A2 D2, ..., An Dn, (integrity-constraint1), , (integrity-constraintk))
r is the name of the relation
each Ai is an attribute name in the schema of relation r
Di is the data type of values in the domain of attribute Ai
Example:
create table instructor ( ID char(5), name varchar(20), dept_name varchar(20), salary numeric(8,2))

19. Integrity Constraints in Create Table
not null
primary key (A1, ..., An )
foreign key (Am, ..., An ) references r
Example:
create table instructor ( ID char(5), name varchar(20) not null, dept_name varchar(20), salary numeric(8,2), primary key (ID), foreign key (dept_name) references department);
primary key declaration on an attribute automatically ensures not null

20. And a Few More Relation Definitions
create table student ( ID varchar(5), name varchar(20) not null, dept_name varchar(20), tot_cred numeric(3,0), primary key (ID),
foreign key (dept_name) references department);
create table takes ( ID varchar(5), course_id varchar(8), sec_id varchar(8), semester varchar(6), year numeric(4,0), grade varchar(2),
primary key (ID, course_id, sec_id, semester, year) ,
foreign key (ID) references student, foreign key (course_id, sec_id, semester, year) references section);
Note: sec_id can be dropped from primary key above, to ensure a student cannot be registered for two sections of the same course in the same semester

21. primary key (course_id),
And more still
create table course ( course_id varchar(8), title varchar(50), dept_name varchar(20), credits numeric(2,0),
primary key (course_id),
foreign key (dept_name) references department);

22. Basic form: (plus many many more bells and whistles)
SQL Query
Basic form: (plus many many more bells and whistles)
SELECT <attributes>
FROM <one or more relations>
WHERE <conditions>

23. Simple SQL Query Product PName Price Category Manufacturer Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
SELECT * FROM Product WHERE category=‘Gadgets’
PName
Price
Category
Manufacturer
Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
“selection”

24. Simple SQL Query Product PName Price Category Manufacturer Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
SELECT PName, Price, Manufacturer FROM Product WHERE Price > 100
PName
Price
Manufacturer
SingleTouch
$149.99
Canon
MultiTouch
$203.99
Hitachi
“selection” and
“projection”

25. Notation Product(PName, Price, Category, Manfacturer)
Input Schema
Product(PName, Price, Category, Manfacturer)
SELECT PName, Price, Manufacturer FROM Product WHERE Price > 100
Answer(PName, Price, Manfacturer)
Output Schema

26. Details Case insensitive: Constants: Same: SELECT Select select
Same: Product product
Different: ‘Seattle’ ‘seattle’
Constants:
‘abc’ - yes
“abc” - no

27. SELECT * FROM Products WHERE PName LIKE ‘%gizmo%’
The LIKE operator
SELECT * FROM Products WHERE PName LIKE ‘%gizmo%’
s LIKE p: pattern matching on strings
p may contain two special symbols:
% = any sequence of characters
_ = any single character

28. Eliminating Duplicates
Category
Gadgets
Photography
Household
SELECT DISTINCT category
FROM Product
Compare to:
Category
Gadgets
Photography
Household
SELECT category
FROM Product

29. Ties are broken by the second attribute on the ORDER BY list, etc.
Ordering the Results
SELECT pname, price, manufacturer
FROM Product
WHERE category=‘gizmo’ AND price > 50
ORDER BY price, pname
Ties are broken by the second attribute on the ORDER BY list, etc.
Ordering is ascending, unless you specify the DESC keyword.

30. ? ? ? PName Price Category Manufacturer Gizmo $19.99 Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
SELECT DISTINCT category
FROM Product
ORDER BY category ? ?
SELECT Category
FROM Product
ORDER BY PName ?
SELECT DISTINCT category
FROM Product
ORDER BY PName

31. Keys and Foreign Keys Company Product CName StockPrice Country
GizmoWorks 25
USA
Canon 65
Japan
Hitachi 15
Key
Product
PName
Price
Category
Manufacturer
Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
Foreign key

32. Join between Product and Company
Joins
Product (pname, price, category, manufacturer)
Company (cname, stockPrice, country)
Find all products under $200 manufactured in Japan; return their names and prices.
Join between Product and Company
SELECT PName, Price FROM Product, Company WHERE Manufacturer=CName AND Country=‘Japan’ AND Price <= 200

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

34. 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

35. A Subtlety about Joins Product (pname, price, category, manufacturer)
Company (cname, stockPrice, country)
Find all countries that manufacture some product in the ‘Gadgets’ category.
SELECT Country FROM Product, Company WHERE Manufacturer=CName AND Category=‘Gadgets’
Unexpected duplicates

36. A Subtlety about Joins What is the problem ? What’s the solution ?
Product
Company
Name
Price
Category
Manufacturer
Gizmo
$19.99
Gadgets
GizmoWorks
Powergizmo
$29.99
SingleTouch
$149.99
Photography
Canon
MultiTouch
$203.99
Household
Hitachi
Cname
StockPrice
Country
GizmoWorks 25
USA
Canon 65
Japan
Hitachi 15
SELECT Country FROM Product, Company WHERE Manufacturer=CName AND Category=‘Gadgets’
What is
the problem ?
What’s the solution ?
Country ??

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

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

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

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

41. 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

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

43. INSERT INTO Product(name) SELECT DISTINCT prodName FROM Purchase
Insertion: an Example
INSERT INTO Product(name)
SELECT DISTINCT prodName
FROM Purchase
WHERE prodName NOT IN (SELECT name FROM Product)
name
listPrice
category
gizmo
100
Gadgets
camera -

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

45. WHERE seller = ‘Joe’ AND product = ‘Brooklyn Bridge’
Deletions
Example:
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.

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