Transcript SQLite - University of Delaware

SQLite
Found Things
• Record a thing (e.g., audio, picture, text,
video, web link, etc.) at a location
• When someone is near the location, perhaps
play the thing.
• Allow things that are played to be selected in
a sophisticate way
– Include various information about the things
• Cache things and get things from the web
Things database
id
type
filename
File
state
lat
long
Recorded
date
Recorded
time
author
score
Last played
Tag 1
Tag 2
1
pic
1.jpeg
here
75..
36..
5/2/2010
1:01
stephan
100
5/3/2010
tree
bird
Look in database and get thing from nearby and that matched other criteria
For now, we will just use near by lat and long
SQLite
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SQLite is a scaled down version of SQL
Data is in tables with rows and columns
Each row is a data entry.
SQL allows data to be stored and retrieved
Basic things (see http://www.w3schools.com/sql/default.asp
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Create database
Create table in the database
Insert data into the table
Get data from table (or tables), via query
There’s other stuff, but this is enough for us
Create database and table
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SQLiteDatabase myDatabase;
myDatabase = openOrCreateDatabase( “/mnt/sdcard/things.db", SQLiteDatabase.CREATE_IF_NECESSARY, null);
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Makes a database called things.db
If no path, then db is in /data/data/<appname>/databases
here we use a specific path so we can examine the db at the command line
Is database already exists, it does not make it
Make table
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Must specify the column name and type (e.g., integer)
Also, there must be a primary column (a key) such that each entry in this column is unique
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One way to do this is to include a column that is an integer that autoincrements
If “IF NOT EXIST” is
missing, then this will crash
if the table already exists
Name of table
myDatabase.execSQL("CREATE TABLE IF NOT EXISTS things" +
"( id INTEGER PRIMARY KEY AUTOINCREMENT," +
" type VARCHAR(40), " +
" filename VARCHAR(40), " +
" lat INTEGER, " +
" long INTEGER);");
Key is named id and is integer
Type is audio, pic, tex, etc.
Filename of the thing
Location of the thing
Try it
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Make function createDatabase
Call createDatabase from onCreate
Run adb
Change to the databases directory
ls
Run sqlite3 things.db “.dump”
Add data
Id of entry
Name of table
long newId = myDatabase.insert("things", null, values);
Set of pairs (column name, data for that column)
ContentValues values = new ContentValues();
values.put("type", "audio");
values.put("filename", "1.mp4");
values.put("lat","75001200");
values.put("long","36000000");
Try it
• Make function insertData()
ContentValues values = new ContentValues();
values.put("type", "audio");
values.put("filename", "1.mp4");
values.put("lat","75001200");
values.put("long","36000000");
long newId = myDatabase.insert("things", null, values);
Log.d(“SQLPlay”,”insert returned id “+newId);
• Run
• adb sqllite3 things.db “.dump”
• Add three buttons
– Record
– Stop
– Play
• Allow record audio, location, internet, camera
Next filename
• We will save the recorded data with name id.mp4, where id is
the id from the database
• So, to determine the filename, we need to get the next id
• Or, insert a partial row, get the id and update the row
id
type
filename
File
state
lat
long
Recorded
date
Recorded
time
author
score
Last played
Tag 1
Tag 2
1
audio
1.mp4
here
75..
36..
5/2/2010
1:01
stephan
100
5/3/2010
tree
bird
2
audio
null
here
76
24
5/3/2010
2:02
stephan
99
5/4/2010
sing
song
id
type
filename
File
state
lat
long
Recorded
date
Recorded
time
author
score
Last played
Tag 1
Tag 2
1
audio
1.mp4
here
75..
36..
5/2/2010
1:01
stephan
100
5/3/2010
tree
bird
2
audio
2.mp4
here
76
24
5/3/2010
2:02
stephan
99
5/4/2010
sing
song
ContentValues values = new ContentValues();
values.put("type", "audio");
values.put("lat“, 36000000);
values.put("long“,74000000);
long newId = myDatabase.insert("things", null, values);
Log.d(“SQLPlay","newId="+newId);
String filename = newId+".mp4";
ContentValues values2 = new ContentValues();
values2.put("filename", Long.toString(newId)+".mp4");
String wheres[] = new String[1];
wheres[0] = Long.toString(newId);
myDatabase.update("things", values2, "id=?", wheres);
Make a new column with the filename empty (null)
Make file name
Make filename column (value pairs like insert)
update
location
• From previous lectures on location
• Add class attribtues
– LocationManager locationManager;
– String provider;
• Make setUpLocation and call from onCreate, after createDatabase
public void setUpLocation() {
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.NO_REQUIREMENT);
locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
provider = locationManager.getBestProvider(criteria, true);
Location location = locationManager.getLastKnownLocation(provider);
String locInfo = String.format("Initial loc = (%f, %f) @ (%f meters up)", location.getLatitude(), location.getLongitude(),
location.getAltitude() );
Log.d("SQLPlay","starting loc: "+locInfo);
}
Get location
Location when not moving/indoors
• Get gps lock since last reboot. That way, .getLastKnownLocation
doesn’t crash
• Add a random number to location
Location location = locationManager.getLastKnownLocation(provider);
Random generator = new Random();
int random1 = generator.nextInt( 1000000 );
int random2 = generator.nextInt( 1000000 );
int latitude = (int)(location.getLatitude()*1E6+random1);
int longitude = (int)(location.getLongitude()*1E6+random2);
• Put this into getNextfileName function
• rm things.db
• Run and make a few files. Dump database
Record sound
• From previous project, cut record sound and
paste into recordSound function
• Cut and paste stopRecording into
stopRecordingButton.onClick
– Make buttons nice
• Run on device
• Make a few entries
adb -d pull /data/data/com.SQLPlay/files c:\audio
adb -d pull /data/data/com.SQLPlay/databases c:\audio
Play sound
• Get location (done)
• Get database entry that is nearest to current
location
– Android query
– SQL SELECT
public Cursor query (String table, String[] columns, String selection, String[]
selectionArgs, String groupBy, String having, String orderBy, String limit)
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Table = “things”
Columns: array of the columns to be returned
– E.g., null, returns all columns
– E.g., String columns[] = “filename”; returns the filename
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{selection selectionArgs} is also know as WHERE (in SQL, one types …. WHERE
~ {selection selectionArgs}
– E.g., selection = “type=?”; String selectionArgs[] = {“audio”}
– E.g., selection = “lat<?”; String selectionArgs[] = {“90000000”}
– E.g., selection = “lat<? AND type=?”; String selectionArgs[] = {“90000000”, “audio”}
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Groupby and having are for grouping (we set as null)
Orderby is to order the replies (we set as null)
Limit controls how many to return (we set as null)
– If orderBy is used, then limit can be used to get the first or first few
– E.g., orderBy = “cost”; limit = “1”; returns the row with the highest cost
Cursor c = myDatabase.query (“things”, null , null, null, null, null, null, null);
cursor
• Cursor is used to get the results, which might be emtpy or have several
rows, where each row has one or more columns
• You can scroll through the cursor
– Also, you should close the cursor when done
– Perhaps use startManagingCursor(c);
c.moveToFirst();
while (c.isAfterLast() == false)
{
String row = new String();
for (int i=0; i<c.getColumnCount(); i++)
row += c.getString(i) + " ";
Log.d("SQLPlay",row);
c.moveToNext();
}
c.close();
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Try it
Make function playAudio and call this function from playButton.onClick
Make function, getfilename
In playAudio, call getFilename
In getFilename, put
Cursor c = myDatabase.query (“things”, null , null, null, null, null, null, null);
c.moveToFirst();
while (c.isAfterLast() == false)
{
String row = new String();
for (int i=0; i<c.getColumnCount(); i++)
row += c.getString(i) + " ";
Log.d("SQLPlay",row);
c.moveToNext();
}
c.close();
Run, select play, and look at log.
Try other selections
String selection = “lat<?”
String selectionArgs[] = {“90000000”};
String selection = “lat BETWEEN ? AND ?”
String selectionArgs[] = {“0”, “90000000”};
String selection = “lat IN ”
String selectionArgs[] = {“somevalue”};
String columns[] = “max(lat)”
Everything else null
String columns[] = “min(abs(lat-70000000))”
Everything else null
Exact match
(maybe somevalue can be a set?)
nearest
• But how to get a nearest point?
– I don’t think it is possible with this type of query
• rawQuery
– Same as SQLite queries.
– Android’s query is easy, but very limited.
rawQuery gives the full power of SQLite
– If you know SQL, then you may as well use
rawQuery
SQL SELECT
• SELECT column_name(s)
• FROM table_name
• WHERE column_name operator value
• SELECT * FROM things WHERE lat < 90000000
• Try in sqlite3
• In shell, # sqlite3 things.db “SELECT * from things” ….
• Smallest lat
– SELECT * FROM things WHERE lat in (SELECT min(lat) )
• Nearest lat to 4000000
• SELECT * FROM things WHERE abs(lat-40000000) in (SELECT
min(abs(lat-40000000) ) );
– Nearest to La, Lo
• SELECT * FROM things WHERE abs(lat - La)+abs(long - Lo) in
(SELECT min(abs(lat - La)+abs(long - Lo) ) );
• Don’t forget spaces, -Lo is an invalid string is Lo<0
Back to code
• Cursor c = myDatabase.rawQuery(…);
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String la = latitude;
String lo = longitude;
String ex = “abs(lat – la) + abs(long – lo)”;
String Q = “SELECT * FROM things WHERE ” +
ex + “ IN ( SELECT min( “ + ex + “) FROM
things) ; “;
• Cursor c = myDatabase.rawQuery(Q, []);
File name
• String Q = “SELECT filename FROM things
WHERE ” + ex + “ IN ( SELECT min( “ + ex + “)
FROM things) ; “;
• Cursor c = myDatabase.rawQuery(Q, []);
• String filename = c.getString(0);
• Log.d(“SQLPlay”,”filename:”+filename);
• Return filename;
Try it
• in getFilename function
Location location = locationManager.getLastKnownLocation(provider);
Random generator = new Random();
int random1 = generator.nextInt( 1000000 );
int random2 = generator.nextInt( 1000000 );
int latitude = (int)(location.getLatitude()*1E6+random1);
int longitude = (int)(location.getLongitude()*1E6+random2);
String la = latitude;
String lo = longitude;
String ex = “abs(lat – la) + abs(long – lo)”;
String Q = “SELECT filename FROM things WHERE ” + ex + “ IN ( SELECT min( “ + ex + “) FROM things) ; “;
Cursor c = myDatabase.rawQuery(Q, []);
String filename = c.getString(0);
Log.d(“SQLPlay”,”filename:”+filename);
return filename;
finally
• In play, paste code to play audio from previous
lecture