In the last lecture you learnt how to upgrade and downgrade your database.
Now that you have a database and a table in place let’s try to understand how to query the database to get data.
Cursor gives you access to the database. In order to use a Cursor you need to use a Query.
To read from a database, use the query() method, passing it your selection criteria and desired columns.
Here is how the query method looks like
query(String table,
String[] columns,
String selection,
String[] selectionArgs,
String groupBy,
String having,
String orderBy,
String limit)
Here is a simple example from the Survey app code base
public Cursor getSurveyData(SQLiteDatabase db){ // Define a projection that specifies which columns from the database you will actually use after this query. String[] projection = { "_id", SURVEY_TABLE_NAME_COLUMN, SURVEY_TABLE_EMAIL_COLUMN, SURVEY_TABLE_AGE_COLUMN }; // How you want the results sorted in the resulting Cursor String sortOrder = "_id" + " DESC"; return db.query( SURVEY_TABLE, projection, null, null, null, null, sortOrder ); }
Please follow the video and refer to the source code.
References
- Android documentation which explains this.
- http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html
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