1. Lecture 8: Database
Topics: Basic SQLite Operations

2. Today’s class: Concepts Database, Table, Primary Key (Lecture)
SQL Commands
Android
(code)
Example of “Characters” database
Create, Insert, Delete, Query

3. Database
Bunch of tables having column headers where you store data—one datum in each row.
Table: Characters
Table: Appearance ID
Name
Home 1
John
Winterfell 2
Tyrion
Casterly Rock 3
Daenerys
Dragon Stone
Episode
CharacterID
Appeared 1 10 2 5 3 7 9
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4. 1. Create and Drop Tables
SQL:
CREATE TABLE Characters ( ID INT PRIMARY KEY, NAME TEXT, HOME TEXT );
Table: Characters ID
Name
Home
SQL:
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DROP TABLE IF EXISTS Characters;

5. 2. Insert and Delete Rows DELETE FROM Characters
SQL:
Table: Characters
INSERT INTO Characters VALUES (1, ‘John’, ‘Winterfell’); VALUES (2, ‘Tyrion’, ‘Casterly Rock’); VALUES (3, ‘Daenerys’, ‘Dragon Stone’); ID
Name
Home 1
John
Winterfell 2
Tyrion
Casterly Rock 3
Daenerys
Dragon Stone
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SQL:
Table: Characters
DELETE FROM Characters
WHERE Name = ‘John’ OR ID = 3; ID
Name
Home 2
Tyrion
Casterly Rock

6. 3. Query (single table)
SQL:
Output:
SELECT ID, Name FROM Characters WHERE ID < 3; ID
Name 1
John 2
Tyrion
SQL:
Output:
SELECT * FROM Characters
WHERE ID < 3; ID
Name
Home 1
John
Winterfell 2
Tyrion
Casterly Rock
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7. 3. Query (multiple table joined)
Table: Characters
SQL: ID
Name
Home 1
John
Winterfell 2
Tyrion
Casterly Rock 3
Daenerys
Dragon Stone
SELECT Name, Episode, Appeared
FROM Characters, Appearance
WHERE ID = CharacterID
AND Episode = 1
AND Appeared < 10
Table: Appearance
Episode
CharacterID
Appeared 1 10 2 5 3 7 9
Output:
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Name
Episode
Appeared
Tyrion 1 5
Daenerys 7

8. Cursor Points to a row of the result of a query.
Used to iterate over the rows: moveToFirst(), moveToNext()
Used to get the value of a specific column: getString(column_index), getInt(column_index), etc.
Output: ID
Name
Home 1
John
Winterfell 2
Tyrion
Casterly Rock 3
Daenerys
Dragon Stone
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9. Android SQLite (in 4 lines)
SQL Operation
Android Programming
Open/Create Database
SQLiteDatabase
db = this.openOrCreateDatabase (“SomeDB", Context.MODE_PRIVATE, null);
Create/Drop Table
Insert/Delete Row
db.execSQL(“ANY SQL COMMAND;”);
Insert Row
(using KEY/VAL pairs)
ContentValues cv = new ContentValues();
cv.Put(KEY, VAL);
db.insert(TABLE, null, cv);
Select
Cursor c = db.rawQuery(“SELECT ….;”, null);
c.moveToFirst();
String s = c.getString(index);
int n = c.getInt(index);
byte[] ba = c.getBlob(index);
c.moveToNext();
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10. Working with Blobs (e.g., image)
SQL Operation
Android Programming
Bitmap to byte[]
ByteArrayOutputStream stream = new ByteArrayOutputStream(); b.compress(Bitmap.CompressFormat.PNG, 100, stream); byte[] ba = stream.toByteArray();
byte[] to Bitmap
Bitmap b = BitmapFactory.decodeByteArray(ba, 0, ba.length);
Insert Row
(using KEY/VAL pairs)
ContentValues cv = new ContentValues();
cv.put(“Name”, “John Doe”);
cv.put(“Photo”, ba);
db.insert(TABLE_NAME, null, cv);
Select
Cursor c = db.rawQuery(“SELECT ….;”, null);
c.moveToFirst();
String name = c.getString(0);
Byte[] ba = c.getBlob(1);
c.moveToNext();
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11. References (study these)