Develop Reference

Adding data to database from program. Android

I faced with the following situation. In my program I have to keep files in database. This database contains title of the article which keeps file and path to the file. All files are kept in Assets folder and are created manually. But what if I want to add files from the program itself. For example to create a special edittexts where user can write title and articles. How can I keep this data? I understand how to add title,entered by user,to database,it's easy. But what about the articles. I can't place them with file which were created manually,as Assets can't keep such files. I thought to add all full articles to database,but how can I add asset's files in such case?

Files (images, PDF'd. Word documents .........) are not structured data and serve little purpose being stored in the database (Full Text Search (FTS) an extension for SQLite is a different matter).
The recommended technique is to store some reference to the file (e.g. full path or perhaps file name (if all files are stored at a location that is discernible by the file name)) in the database. So when you locate/search and obtain a row you then use the file itself.
However, if the files average around about 100k or less then SQLite can actual be faster and thus it may performance wise, be better to store the files in the database.
Note the 100k based upon the link below.
35% Faster Than The Filesystem
You would store files as BLOB's (byte arrays). You read them into a byte array and on Android, assuming java and that the byte array is named my_byte_array and that the SQLiteDatabase is db then :-
ContentValues cv = new Contentvalues();
cv.put("FILE_COLUMN",my_byte_array);
........ other cv.put's for the other columns
long inserted_id = db.insert("The_Table",null,cv);
if (inserted_id < 1) {
.... code to handle row not inserted.
} else {
.... code to handle row inserted OK
}
WARNING
Files greater than 2M will be impossible to easily retrieve as a Cursor Window is limited to 2M of memory. Even 1M may well cause issues and may be unusable at some stage if the App needs to be backwardly compatible as I believe that Cursor window's were restricted to 1M (not sure when).
Retrieval from the database
To retrieve data from a BLOB you use the Cursor getBlob(column_offset) method, or generally better use the Cursor getColumnIndex(column_name) method to retrieve the column offset according to the column name. So if the Cursor is named csr then** my_other_byte_array = csr.getBlob(csr.getColumnIndex(column_name));**
Noting that you have to move to a valid row before using the getBlob method.

I would like to create a database containing 600 text files for an android Application

I have 600+ text files. How do I put them in a database, with mySQL lite.
I want to have 3 columns: index(1 to 600), title and content.
How do I do that? Thanks.

http://www.sqlite.org/datatype3.html
When you create the database (the single table in it), the index should be auto-generated when the entry is created in the table (if you properly created the table with auto indexing)
I would use TEXT (varchar) for the title & blob for the actual text file (the data in it).
The previous answer seems to put you on the right track, though I'm not sure I quite understand how you intend to actually populate the table with the data.

Use content provider for android below is nice link.
http://www.vogella.com/tutorials/AndroidSQLite/article.html.
For datatype to use integer,text,text as columns, below is
datatype link of sqlite.
http://www.sqlite.org/datatype3.html
But Instead of storing the file data in sqlite, I would suggest you to store sdcard path of files in sqlite table and retreive from sdcard when required.
In above case columns will be index,title,filepath.

Changing a Column type in my Android App's Database

I have an app published in the play store.
The app uses a database which holds a table which has a column of type int.
I'm doing a new change where I need to change the column type to long.
How do I go about handling it in the DatabaseHandler I'v created.
I want to preserve the data stored in the older apps database, so what should ideally be the code in the onUpgrade() function???

You don't need to change the database column type. An INTEGER column will happily contain all the bits needed to represent a Java long.
In fact, there's no long column type in sqlite.

I think using SQLite, the best way is to create a temporary table, copy all your table content, drop the old table and recreate the table with the right type on your column, then you can just copy the content from the temporary table and drop it...
I know this don't fell like the best approach, but I don't think SQLite have some alter table function.

As far I know you can t do this . But You can drop your table if it exists and create it again . Maybe you can find out some useful information here SQLite Modify Column or here Modify a Column's Type in sqlite3

A .txt to modifiable android database

I have a question for you guys.
I have been working on a project application that in one part uses an SQLite database loaded from a txt file (it has about 100k-200k rows of 5 strings separated by the ^ sign).
Now my question is, since this is my first time working with databases, how does .txt import for modifiable databases work? If I understand right, it pulls all data from the txt file once and creates a database that it keeps to work on, so when I modify the database I modify the newly created one and not the txt? Does the code try to pull info again from the txt whenever the app loads, and would loading 200k 10char words every time be too much? :)
The database consists of music bands in this format: name/genre/popular[yes/no]/selected
The selected column is the only one being modified by the user (and the app for that matter). If I use the regular approach to databases with added implementation from a txt file will the selected column reset every time (do not want that)?

Don't distribute your app with a huge txt-file and import it on the users device. This takes time and is annoying.
Rather distribute your app with a pre-populated database and copy it over from the res-folder. You can use android-sqlite-asset-helper to automate this.
Also, yes. The Database is always stored on the internal memory and you can't access it on a non-rooted device (unless you're using the AVD).
To import your txt-contents into a database, create a script or something that parses the contents and executes the corresponding SQL-queries. Again, your App should ship with the database, not the raw-file!
I was a little bored and hacked together a short Python-Script to read all entries from your txt-file and insert them into a SQLite Database:
import sqlite3
import re
counter = 0;
pattern = re.compile('^([^\^]+)\^([\w\s]+)\^(yes|no)\^\w+$');
conn = sqlite3.connect("imported.db");
cursor = conn.cursor();
# Create the Table:
conn.execute('''
CREATE TABLE Bands (
name TEXT,
genre TEXT,
popular INTEGER,
selected INTEGER
);''');
# Now, insert:
with open('bands.txt', 'r') as f:
for line in f:
match = pattern.search(line);
if match:
cursor.execute('''
INSERT INTO Bands (name, genre, popular, selected)
VALUES (?,?,?,0)''',
(
match.group(1), match.group(2),
(1 if match.group(3) == 'yes' else 0)
)
);
counter+=1;
conn.commit();
conn.close();
print "Imported ", counter, " bands!";
This will assume that the txt-file is named bands.txt, each value is separated by a / and each entry will be on it's own line. The resulting database-file is imported.db.
Also, I use INTEGER for all True|False-fields (popular, selected). These will then hold a 0 for false and a 1 for true.
Last but not least, the RegEx only allows "yes" and "no" for the popular-value.

Empty tables size in sqlite db

I am creating a db for my android app which requires different tables for different types of users. Basically, if user type A logs in he will use Table A, user type B logs in he will use Table B and similarly Table C.
Should I go ahead and create 3 tables and use only the table which the user type has logged in? Would this have any significant memory implications (size of the db)? That is, if the table doesn't contain data, would the sqlite db still allocate some space (other than for definitions of the columns).
The other way would be to check the user type and dynamically create the table at runtime once user logs in. I prefer the first method if there isn't much space used.
Any pointers or suggestions would be very useful.

The SQLite DB will occupy some space to store the table structures and the constraints/indexes. Why don't u just create the database tables (w/o any data) using SQLite Browser and check the size of the database file.
Would help you decide.

I think instead of creating all tables at one go use SQL queries to create tables as and when needed. If its not needed anymore you can even drop the table.