Develop Reference

Android sqlite - how to calculate the difference between 2 REAL entries in sqlite?

In Android/Java, I am trying to compute and store the difference between 2 values in sqlite when one value is entered.
My table looks like this:
When weights are added/stored in the table in the column 'Weight', the column 'Diff_Weight' shall receive "Weight(N) - Weight(N-1)". Example: the last cell of Diff_Weight (row 6) = 88.0 - 55.2 = 32.8. // Row 5 shall get '-0.7' etc. Their type is REAL (col Weight & col Diff_Weight).
This 32.8 should be calculated and added at the same time when 88.0 is added to the table.
So far, I have read lots of tutorials and can't figure how to proceed. (My code to create and insert in the DB is fine, but reading is somehow more complex).
My code to read the entry is very bad because I don't see how to set it up:
public Bouble getData() {
String selectQuery= "SELECT * FROM " + TABLE_NAME2 + " ORDER BY COL_4 DESC LIMIT 1";
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(TABLE_NAME2, null);
result2 = Double.valueOf(cursor.getString(cursor.getColumnIndex("Weight")));
result1 = Double.valueOf(cursor.getString(cursor.getColumnIndex("Weight")-1));
insertdata(result2-result1); //insert in row 6 of Diff_Weight
return
}
Can anybody help there?
If that is unclear, I was needing some help for the sqlite command AND the java to get the difference result.

Simplistically you can get the data by joining to the same table
SELECT a.id, a.weight, b.weight, (b.weight - a.weight) FROM TABLE_NAME2 a
join TABLE_NAME2 b on (b.id = a.id + 1);

One way is to use the lag() window function to get the value of the previous row (As ordered by id; using timestamps would be better but between splitting up the date and time into different columns and not using a date format that can be meaningfully sorted, this is easier.):
SELECT id, weight,
round(coalesce(weight - lag(weight, 1) OVER (ORDER BY id), weight), 1) AS diff_weight
FROM example
ORDER BY id
which gives
id weight diff_weight
---------- ---------- -----------
1 22.0 22.0
2 22.2 0.2
3 55.0 32.8
4 55.9 0.9
5 55.2 -0.7
6 88.0 32.8
You can make a view of this query use that like a normal table if you like. Generating the differences dynamically like this has the advantage that if an existing weight value changes, everything that depends on it doesn't have to be updated.

ok, after a long search, here is a possible result (sqlite + java):
first, you need to query the last row of the table...
...and handle the case if there is no row in your table (blank or new table)
then you must query the 'Weight' value from the known column 'Weight' (Y) and the row with ID you already have (X)
and when you have your value (last_weight), you need to write the difference (weight-last_weight) in the column 'Diff_Weight'.
Here is the code:
SQLiteDatabase db = this.getWritableDatabase();
//query the last row of the table
Cursor cursor = db.rawQuery("SELECT ID FROM TABLE_NAME2 ORDER BY ID DESC LIMIT 1", null);
cursor.moveToLast();
int lastID;
//handle the case if there is no row in your table
try {
lastID = cursor.getInt(0);
} catch (Exception e) {
lastID = 0;
}
Double lastWeight = 0.0;
//query the 'Weight' value
if (lastID >= 1) {
Cursor cursor2 = db.rawQuery("SELECT Weight FROM TABLE_NAME2 WHERE ID=" + lastID, null);
if (cursor2.moveToFirst()) { //this is boundary otherwise 'lastWeight' doesn't get the value
lastWeight= cursor2.getDouble(0);
}
} else {
lastWeight = 0.0;
}
//write the difference in the Diff_Weight column (=COL_5)
ContentValues cValues2 = new ContentValues();
//add your data in COL_1 to COL_4 here...
cValues2.put(COL_5, weight - lastWeight);
long id2 = db.insert(TABLE_NAME2, null, cValues2);
... And so you get the red figures in the column Diff_Weight from the table photo in the question.

Android SQLite rawQuery - How to select multiple rows of a table

I'm trying to use rawQuery to return a cursor with a few different rows of data to be passed into it. When there is only 1 argument it works. When there is more than 1 argument it displays the empty ListView state. I believe the issue lies here:
// Query for items from the database and get a cursor back. Edited code for clarity:
recipeCursor = db.rawQuery("SELECT course, name, _id " +
" FROM recipes WHERE _id = ?",
selectedRecipesSQL);
When the code works the selectedRecipesSQL would look something like:
String[] selectedRecipesSQL;
selectedRecipesSQL = new String[]{"2"};
And when it doesn't work it would be something like
String[] selectedRecipesSQL;
selectedRecipesSQL = new String[]{"2 OR 5"};
So, to be clear, I can display a single row of the table in my ListView, but if I try to display more than one row of the table then it won't display anything.
One ugly solution which has crossed my mind (but I haven't pursued) is that I need to edit the rawQuery selection statement to read something like:
recipeCursor = db.rawQuery("SELECT course, name, _id " +
" FROM recipes WHERE _id = ? OR _id = ? OR _id = ?",
selectedRecipesSQL);
I'd probably use a for loop to generate the correct amount of WHERE "_id = ?" and then use a string array:
selectedRecipesSQL = new String[]{"2", "5"};

One way of doing it is by passing the possible values of _id as 1 string which is a comma separated list like this:
selectedRecipesSQL = new String[]{"1,2,3"};
and in your query use the operator LIKE:
recipeCursor = db.rawQuery(
"SELECT course, name, _id FROM recipes WHERE ',' || ? || ',' LIKE '%,' || _id || ',%'",
selectedRecipesSQL
);
This works also for just 1 value.

static String multiply__concat_string(String text,String joiner_,int multiple_)
{
String output="";
for(int i=0;i<multiple_;i++)
{
output+=(text+joiner_);
}
if(output.length()>0)
{
output=output.substring(0,output.length()-1);
}
return output;
}
Use it like this :
selectedRecipesSQL = new String[]{"2", "5"};
db.rawQuery("SELECT course, name, _id " +
" FROM recipes WHERE _id IN("+multiply_concat_string("?",",",selectedRecipesSQL.length)+")",
selectedRecipesSQL);

How to get Data from getAll() method inside an Activity

Database structure:
Detail table
rid name
1 Beta
2 Release
Record table
recid rname conrid (conrid is rid from Detail table)
1 App1 1
2 App2 1
3 App3 2
4 App4 1
I have written a method to get all the data from both the tables (Detail and Record) based on rid and conrid.
Here is the code:
String select = "SELECT rname FROM " + TABLE_RECORD+ " where conrid =" +detail.getId();

It seems you are closed in a loop where you're byting your tail...
So, I'll mix together your code with the answer provided by #MD.
I'm confident he doesn't take it bad. ;)
You will need to add a Class named RecDet (containing the Name field from Detail and RName from Record).
Use that one in place of Detail and Record.
// to get all data from Detail and Record tables
public List<RecDet> getAll()
{
List<RecDet> listRecDet = new ArrayList<RecDet>();
// Select All Query
String selectQuery =
"SELECT Details.name, Record.rname FROM Detail INNER JOIN Record " +
"ON Record.conrid = Detail.rid";
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor != null && cursor.moveToFirst())
{
do
{
RecDet recdet = new RecDet();
recdet.setName(cursor.getString(cursor.getColumnIndex("name")));
recdet.setRname(cursor.getString(cursor.getColumnIndex("rname")));
listRecDet.add(recdet);
} while (cursor.moveToNext());
}
return listRecDet;
}

Let's try this
select Details.name,Record.rname from Detail INNER JOIN Record ON Record.conrid=Detail.rid

How to swap values in columns SQLite?

I have table ( id , text) and I need to swap two values in columns like this:
Before.
1 one.
2 two.
3 three.
After ( 1 and 3 swap)
1 three
2 two
3 one

To update each row, you need something like this:
void updateMyTableText (MyTableRow row)
{
ContentValues values = new ContentValues();
values.put ("text", MyTableRow.text);
String where = "id = ?";
String[] whereArgs = new String[1];
whereArgs[0] = Long.toString (row.id);
getDb().update ("MyTable", values, where, whereArgs);
}
where MyTableRow is
class MyTableRow
{
long id;
String text;
}
You'll also need some queries to get the "text" for rows 1 and 3.
Here's one way to do a query:
long getId (String text)
{
// do the query
String query = "select id from MyTable where text = ? ";
String[] args = new String[1];
args[0] = text;
Cursor cursor = getDb().rawQuery (query, args);
if (cursor == null)
throw new IllegalStateException ("cursor is null");
try
{
// get the results
if (!cursor.moveToNext())
return -1; // row not found
long id = cursor.getLong (0);
return id;
}
finally
{
cursor.close();
}
}

Are you trying to change the values in the rows themselves? Most databases systems don't let you arbitrarily swap values since there is an assumption that they are permanently associated. You could issue UPDATE commands to permanently modify the values, but doing this temporarily will probably be an issue handled once the data is returned.
UPDATE table_name
SET text=three
WHERE id=1;
UPDATE table_name
SET text=one
WHERE id=3;

// Assuming id1 < id2
void swap(id1,id2)
{
SQLiteDatabase db = this.getWritableDatabase();
ContentValues CV = new ContentValues();
// First get the 2 rows
Cursor res = db.rawQuery("SELECT COLUMN_NAME FROM "+ TABLE_NAME +" WHERE ID IN ("+id1+","+id2+") ORDER BY ID ASC",null);
res.moveToFirst();
CV.put("COLUMN_NAME",res.getString(0));
//Update 1st row with 2nd item
db.update(TABLE_NAME,CV,"ID = ?",new String[]{id2+""});
res.moveToNext();
CV.put("COLUMN_NAME",res.getString(0));
//Update 2nd row with 1st item
db.update(TABLE_NAME,CV,"ID = ?",new String[]{id1+""});
}
Hope it helps!!

How to get Group ID of contacts Number (Android)

How to get Group ID knowing contact's Number
I guess it have to be another query inside this one, but I have not ANY idea how to do it
Here what I've tried:
String[] projection = new String[]{ ContactsContract.Groups._ID };
Cursor cursor = getContentResolver().query(
ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
projection,
ContactsContract.CommonDataKinds.Phone.NUMBER +" = "+ number,
null,
null);
cursor.moveToNext();
String id = cursor.getString(cursor.getColumnIndex(ContactsContract.Groups._ID));
(Query returns nothing)
Thanks for help!

Your query returns nothing, because there is no such column Groups._ID within dataset CommonDataKinds.Phone.
Try something like this:
String sPhoneNumber = "+48123456789";
Cursor cursor = getApplicationContext().getContentResolver().query(
Data.CONTENT_URI, new String[] {CommonDataKinds.GroupMembership._ID},
ContactsContract.CommonDataKinds.Phone.NUMBER+"='"+sPhoneNumber+"'", null, null);
where sPhoneNumber is String with desired phone number. Keep in mind, that your cursor may still return 0 depending on:
how your phone number is formatted, i.e. you wish to find group ID
for contact of given number +49123456789 while number is formatted
like this +49 123 456 789. Whitespaces are making this completely
different String.
your contact does not belong to any group.
Also cursor can still return more results, mostly in cases when your contact belongs to more than one group.