Develop Reference

Fetch Date from database that is shipped with android app

I am following this tutorial http://mobisys.in/blog/2012/01/tutorial-using-database-in-android-applications/ to have an external database with my android app.
I am not able to apply where clause while fetching the data from the database.
This is what I have done so far.
c=myDbHelper.query("level1", null, "_id=2", null, null,null, null);
if(c.moveToFirst())
{
do {
Toast.makeText(Level1.this,
"_id: " + c.getString(0) + "\n" +
"name: " + c.getString(1) + "\n"
,
Toast.LENGTH_LONG).show();
} while (c.moveToNext());
}
The databaseHelper class
public Cursor query(String table,String[] columns, String selection,String[] selectionArgs,String groupBy,String having,String orderBy){
return myDataBase.query("level1", null, "_id", null, null, null, null);
}
Can anyone help me with this?

You pass "_id=2" as selection when calling myDbHelper.query. But in your DB Helper query method, selection is never used (same goes for other parameters).
You probably want to change query to something like:
public Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy){
// double check parameters I did type that here (no IDE)
return myDataBase.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
}
See also, the documentation of SQLiteDatabase

SimpleAdapter needs an _id field

I got this :
Cursor c = db.query("Org", null, null, null, null, null, null);
which means I choose a table "Org", but together with this I need to make this :
Cursor c = db.rawQuery(" SELECT "+ id + " AS _id")
because SimpleAdapter need to have an _id field necessarily for some reason or it will crash with an error. How do I combine this 2 into one query?

The second parameter of the query function is the list of columns.
If you want to rename a column, you cannot just blindy return all columns but have to list the desired columns:
String[] columns = new String[] { id+" AS _id", "Name", "Color", "whatever..." };
Cursor c = db.query("Org", columns, null, null, null, null, null);

For your statement : Cursor c = db.query("Org", null, null, null, null, null, null); the second parameter is wrong, you shoukd mention the column names in it.
public Cursor query (boolean distinct, String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit)
Whereas for,
Cursor c = db.rawQuery(" SELECT "+ id + " AS _id from Org");
means that you Select id and create an alias of it using AS into _id, and you are selecting this id from Org table.
so now you will be able to access the result from this query from the column name _id, and in order to access the result use:
c.moveToFirst();
while (c.moveToNext())
{
System.out.println(c.getString(c.getColumnIndex("_id"));
}

Query only the first data from a table

I'm trying to query only the first data from the table.
Cursor img_cursor = db.query(
IMAGE_URL_TABLE_NAME,
new String[]{"small_img_url" , "large_img_url"},
null",
null, null, null, null);
Could somebody tell me how to implement a query where only the first data is retrieved from a table?
Solution
I think I solved the answer:
Cursor img_cursor = db.query(
IMAGE_URL_TABLE_NAME,
new String[]{"small_img_url" , "large_img_url"},
null",
null, null, null, null , "1");
I used limit 1 first, but the application crashed. Only if I pass the number as a String will it work. The query has 8 parameters while we're using the limit parameter.

limit 1
From Documentation:
public Cursor query (boolean distinct, String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit)
so, put your last argument to be "limit 1".
Cursor img_cursor = db.query(
IMAGE_URL_TABLE_NAME,
new String[]{"small_img_url" , "large_img_url"},
null,
null, null, null, "limit 1");

How to perform an SQLite query within an Android application?

I am trying to use this query upon my Android database, but it does not return any data. Am I missing something?
SQLiteDatabase db = mDbHelper.getReadableDatabase();
String select = "Select _id, title, title_raw from search Where(title_raw like " + "'%Smith%'" +
")";
Cursor cursor = db.query(TABLE_NAME, FROM,
select, null, null, null, null);
startManagingCursor(cursor);
return cursor;

This will return you the required cursor
Cursor cursor = db.query(TABLE_NAME, new String[] {"_id", "title", "title_raw"},
"title_raw like " + "'%Smith%'", null, null, null, null);

Alternatively, db.rawQuery(sql, selectionArgs) exists.
Cursor c = db.rawQuery(select, null);

This will also work if the pattern you want to match is a variable.
dbh = new DbHelper(this);
SQLiteDatabase db = dbh.getWritableDatabase();
Cursor c = db.query(
"TableName",
new String[]{"ColumnName"},
"ColumnName LIKE ?",
new String[]{_data+"%"},
null,
null,
null
);
while(c.moveToNext()){
// your calculation goes here
}

I came here for a reminder of how to set up the query but the existing examples were hard to follow. Here is an example with more explanation.
SQLiteDatabase db = helper.getReadableDatabase();
String table = "table2";
String[] columns = {"column1", "column3"};
String selection = "column3 =?";
String[] selectionArgs = {"apple"};
String groupBy = null;
String having = null;
String orderBy = "column3 DESC";
String limit = "10";
Cursor cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy, limit);
Parameters
table: the name of the table you want to query
columns: the column names that you want returned. Don't return data that you don't need.
selection: the row data that you want returned from the columns (This is the WHERE clause.)
selectionArgs: This is substituted for the ? in the selection String above.
groupBy and having: This groups duplicate data in a column with data having certain conditions. Any unneeded parameters can be set to null.
orderBy: sort the data
limit: limit the number of results to return

Try this, this works for my code
name is a String:
cursor = rdb.query(true, TABLE_PROFILE, new String[] { ID,
REMOTEID, FIRSTNAME, LASTNAME, EMAIL, GENDER, AGE, DOB,
ROLEID, NATIONALID, URL, IMAGEURL },
LASTNAME + " like ?", new String[]{ name+"%" }, null, null, null, null);

data type mismatch error when using ORDER BY

I've got an android app using a local sqlite database.
private SQLiteDatabase mDb;
when I run this query I get my Cursor over rows with pid equal to id, as desired:
mDb.query(true, PT_TABLE, new String[] {KEY_PID, KEY_TID},
KEY_PID+" = "+id, null, null, null, null, null);
when I run the following query, aiming to get that same result set, ordered by pid I get "android.database.sqlite.SQLiteException: datatype mismatch"
mDb.query(true, PT_TABLE, new String[] {KEY_PID, KEY_TID},
KEY_PID+" = "+id, null, null, null, null, KEY_PID+" DESC");
Any ideas?

It looks like you got just a little mixed up. According to the SQLiteDatabase.query documentation, the last argument is the LIMIT clause. The second to last is the ORDER BY clause.
Cursor query (boolean distinct,
String table,
String[] columns,
String selection,
String[] selectionArgs,
String groupBy,
String having,
String orderBy, // <-- ORDER BY
String limit)
EDIT
But, there is also another SQLiteDatabase.query where ORDER BY would be last
Cursor query (String table,
String[] columns,
String selection,
String[] selectionArgs,
String groupBy,
String having,
String orderBy)

This worked for me
String filter = MySQLiteHelper.JOB_ID + "=" + Integer.toString(jobID);
String orderBy = MySQLiteHelper.LOG_TIME + " DESC";
Cursor cursor = database.query(MySQLiteHelper.LOG_TABLE_NAME, logTableColumns,
filter, null, null, null, orderBy);

KEY_PID + " = " + "'" + id + "'"

Since Orderby is the second last parameter in the query;
your query would be like this
mDb.query(true, PT_TABLE, new String[] {KEY_PID, KEY_TID},
KEY_PID+" = "+id, null, null, null, KEY_PID+" DESC", null);

If I correctly understood your problem, try this.
String[] columns = new String[] {KEY_PID, KEY_TID};
String where = KEY_PID + " = " + Integer.toString(id);
String orderBy = KEY_PID + " DESC";
Cursor cursor = mDb.query(PT_TABLE, columns, where, null, null, null, orderBy);