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Android SQLite add new table on upgrade

I would like to update my database and add a new table. So following this Stackoverflow question, I have incremented my database from version 1 to version 2. Then in onUpgrade, I wrote the code to add new table and insert data:
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (oldVersion < 2) {
String CREATE_B_TABLE = "CREATE TABLE IF NOT EXISTS b ( " +
"_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
"qset TEXT, "+
"highscore TEXT )";
db.execSQL(CREATE_B_TABLE);
String ADD_B = "INSERT INTO b ( qset ) VALUES ('1B'), ('2B'), ('3B'), ('4B'), ('5B'), ('6B'), ('7B'), ('8B'), ('9B'), ('10B')";
db.execSQL(ADD_B);
}
this.onCreate(db);
}
I also put the same code in onCreate to cater for new users.
However, something weird happened when the app is upgraded. The Add_B is inserted twice to the table, so I am having duplicated data. If I removed the code in onUpgrade, new table is added without duplication. It seem like onCreate is called when the app is upgraded, contradicting with the answer from another stackoverflow question.

If I read correctly the code you are intentionally calling the onCreate method from your onUpgrade.
Just before the method ends you call: this.onCreate(db)

Green Dao onUpdate. How can I add new columns to old tables?

When using green dao there is some code customisation needed for updating from one schema to the next. For my earlier needs it was sufficient to add any new tables using code like this in DaoMaster.java:
if(oldVersion==SCHEMA_VERSION_OLD_VERSION&& newVersion==SCHEMA_VERSION){
Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by adding language & checklist table");
boolean ifNotExists = true;
NewTableDao.createTable(db, ifNotExists);
NewTable2Dao.createTable(db, ifNotExists);
}
And so far it's worked great. However for my current schema I have added more connections between the tables, and after updating from the old version, I get crashes indicating that the new columns don't exist.
Is there a way in greendao to add new columns? do I need to write the sqlite code in a old school fashion to get this going?
(Any code samples are A LOT of welcome)
Thanks in advance

Have a look at the SQL code for creating your table (located in the DAO-class).
Extract the relevant change in the SQL.
Update your exiting table manually.
Example:
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i(TAG, "Update Schema to version: "+Integer.toString(oldVersion)+"->"+Integer.toString(newVersion));
switch (oldVersion) {
case 1:
/* v1->v2: all changes made in version 2 come here */
db.execSQL("ALTER TABLE "+MyDao.TABLENAME+" ADD COLUMN 'NEW_COL_1' INTEGER;");
db.execSQL("DROP TABLE IF EXISTS 'MY_OLD_ENTITY'");
/* break was omitted by purpose. */
case 2:
/* v2->v3: all changes made in version 3 come here */
MyNewDao.createTable(db, true);
db.execSQL("ALTER TABLE "+MyDao.TABLENAME+" ADD COLUMN 'NEW_COL_2' TEXT;");
/* break was omitted by purpose. */
}
}

Why does SQLiteOpenHelper drop the table in "onUpgrade" method?

I learned a way which use SQLite3 on Android OS recently.
But it has a non acceptable part.
I can't understand why drop the table when called "onUpgrade" method of SQLiteOpenHelper.
Why need "onUpgarde" method?
If code executes "drop table", table data of old version DB will be removed, isn't it?
Why delete existing data of old DB?
How to restore existing DB data when drop the table?
[Here is learned code]
public class MySQLiteOpenHelper extends SQLiteOpenHelper {
final String CONFIRMED_SHEETS_TABLE = "confirmed_sheets";
public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
#Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String sql = "create table" +
CONFIRMED_SHEETS_TABLE +
"_id integer primary key autoincrement, " +
"group text, " +
"num001 text, " +
"num002 text, " +
"num003 text, " +
"num004 text, " +
"num005 text, " +
"num006 text, " +
"date text)";
sqLiteDatabase.execSQL(sql);
}
#Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
// non acceptable part //
String sql = "drop table if exists " + CONFIRMED_SHEETS_TABLE;
sqLiteDatabase.execSQL(sql);
onCreate(sqLiteDatabase);
}
}

If code executes "drop table", DB table data of old version DB will be
removed, isn't it?
Yup
Why need "onUpgrade" method?
If you are switching databases (for example because you added a new column), your app (usually) now depends on that change. Increasing the database version in your Helper class calls onUpgrade(), which allows you to take care of any migration to prepare the app to use your new schema.
Did you know why learned code executes "drop table"?
Convenience. It's not necessarily the right approach, but a database change can make it hard to take old data and merge it in the new table. Thus, it is easier logic-wise to simply start anew.
If you want to merge an existing and new table, have a look at this question.

You do not need to perform a DROP TABLE in onUpgrade(), as it is currently written in your code. The purpose of onUpgrade() is for your app to check if a new version of your app's database is being installed on a user's device, and if so, if there are any changes to your database, such as adding a new column, you can make those changes within onUpgrade(). If you never change your database schema, you never need to do anything in onUpgrade().
For more information and a introductory tutorial on Databases in Android, refer to the Notepad sample code here.
EDIT: also, here's an example of an onUpgrade() I wrote for one of my apps:
/**
* Handle upgrades to the database.
*/
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if(DBG) Utils.log(TAG, "DBHelper: onUpgrade()...");
// Logs that the database is being upgraded
Utils.log(TAG, "w", "Upgrading database from version " + oldVersion + " to "
+ newVersion);
/*
* Every time you add new columns to the database in the phone, you will want
* to increment the Database version above and then add a condition in here for
* upgrading to it. Otherwise it will cause upgrading users to be nontrivial and
* lead to unnecessary crashes or upgrade instructions.
*/
if (newVersion > oldVersion && newVersion <= 4) {
db.execSQL("ALTER TABLE " + TrackerDb.SomeTable.TABLE_NAME + " ADD COLUMN "
+ TrackerDb.SomeTable.COLUMN_NAME_DATE_MODIFIED + " TEXT");
}
}

OnUpgrade() is called when db versions "old and new" does not match; which means that the user wants to change Database Structure (Dropping a table, Adding new Table, Modifying Table definition).
So the OnUpgrade() should contain the logic as:
Take Backup of the existing data (e.g. Generate insert statements for existing
data).
Modify Database Structure accordingly.
Restore the data from the backup.

How to make dynamic column using Android SQLite Database

Im writing application on Android and im using SQlite database.
I want to be able to add columns to my table by the user choice.
so the user can add any column that he wants the to table. For example the user have "animal" table and he want to add column for "dog", "cat" and "fish".
I have read about some solutions and i didnt saw one that can help me.
I read that the simple way to add column is using:
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// If you need to add a column
if (newVersion > oldVersion) {
db.execSQL("ALTER TABLE " + TableName + " ADD COLUMN " + ColumnName);
}
}
But my problem with this that i cant choose what is the name of the column that will be added to the table by the user choise, there is no parameter for string.
So i tried using something like this, and to call it directly.
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion, String newColumnName) {
// If you need to add a column
if (newVersion > oldVersion) {
db.execSQL("ALTER TABLE " + TableName + " ADD COLUMN " + newColumnName);
}
}
But i got error for this method.
I have another question about the database version.
The onUpgrade method get automaticly called when onCreate get called.
In onUpgrade there is oldVersion and newVersion parameters for the database version. when do i set the oldVersion and newVersion parameters? How i set my newVersion parameter to 2,3,4...?

You can create an auxiliary table to hold the extra column data. Queries to your primary table can be converted into queries on a new view.
create table if not exists animal (pk integer primary key, name);
create table if not exists animal_aux (animal_pk, col_name, col_val);
create view if not exists animal_view
as select animal.name as name,
ct.col_val as cat,
dt.col_val as dog
from animal, animal_aux as ct, animal_aux as dt
where animal.pk = ct.animal_pk
and animal.pk = dt.animal_pk
and ct.col_name = 'cat'
and dt.col_name = 'dog'
;
This schema should be enhanced to make animal_pk, col_name a primary key, or at least unique in animal_aux. You may also need triggers to add or remove entries in the aux table when you insert or delete entries in the animal table.
Example:
sqlite> select * from animal_view;
sqlite> insert into animal values (NULL, 'fred');
sqlite> select * from animal_view;
sqlite> select * from animal;
1|fred
sqlite> insert into animal_aux values (1, "dog", "beagle");
sqlite> insert into animal_aux values (1, "cat", "siamese");
sqlite> select * from animal_view;
fred|siamese|beagle
sqlite>
Each time you add a virtual column, you'll need to
drop view animal_view;
and then re-create it with the appropriate extra columns and where clauses.

final static String Database_name="empDb.db";
public DatabaseHelper(Context context) {
super(context, Database_name, null, 1);
}
#Override public void onCreate(SQLiteDatabase db) {
db.execSQL("create table emp_tbl (id INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT,salary TEXT)");
}
#Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS tbl_emp");
}
blog: https://itmulc.blogspot.com/2016/08/android-sqlite-database-with-complete.html
Get more info about it.
https://www.youtube.com/watch?v=W8-Z85oPNmQ

Android SQLite Upgrade without losing data

I have created a SQLite database successfully and it works fine. However when the onUpgrade method is called, I'd like to do so without losing data. The app I'm developing is a quiz app. Simply, when the onCreate method is called I create and prepopulate a database with questions, answers etc. The last column is whether they have set the question as a favourite or not. What I would like to do is that when the onUpgrade method is called, I'd like to temporarily save that one column, drop the whole database, recreate it with any edits I've made to old questions and add any new questions then re-add back the questions that they set as favourites.
So one option I tried was the following:
db.execSQL("ALTER TABLE quiz RENAME TO temp_quiz");
onCreate(db);
db.execSQL("INSERT INTO quiz (favouries) SELECT favourites FROM temp_quiz");
db.execSQL("DROP TABLE IF EXISTS temp_quiz");
However this doesn't work owing to the fact INSERT INTO just adds new rows rather than replacing the existing rows. I have also tried REPLACE INTO, INSERT OR REPLACE INTO and
db.execSQL("INSERT INTO quiz (_id, favouries) SELECT _id, favourites FROM temp_quiz");
of which none work.
Currently I do have it set up to work by altering the name of the table, calling the onCreate(db) method and then setting up a cursor which reads each row and uses the db.update() method as shown below:
int place = 1;
int TOTAL_NUMBER_OF_ROWS = 500;
while (place < TOTAL_NUMBER_OF_ROWS) {
String[] columns = new String[] { "_id", ..........., "FAVOURITES" };
// not included all the middle columns
Cursor c = db.query("temp_quiz", columns, "_id=" + place, null, null, null, null);
c.moveToFirst();
String s = c.getString(10);
// gets the value from the FAVOURITES column
ContentValues values = new ContentValues();
values.put(KEY_FLAG, s);
String where = KEY_ROWID + "=" + place;
db.update(DATABASE_TABLE, values, where, null);
place++;
c.close();
}
However whilst this works it is extremely slow and will only get worse as my number of questions increases. Is there a quick way to do all this?
Thank you! P.S. Ideally it should only update the row if the row is present. So if in an upgrade I decide to remove a question, it should take this into account and not add a new row if the row doesn't contain any other data. It might be easier to get it to remove rows that don't have question data rather than prevent them being added.

changed it to:
db.execSQL("UPDATE new_quiz SET favourites = ( SELECT old_quiz.favourites
FROM old_quiz WHERE new_quiz._id = old_quiz._id) WHERE EXISTS
( SELECT old_quiz.favourites FROM old_quiz WHERE new_quiz._id = old_quiz._id)");
Which works :D

public class DataHelper extends SQLiteOpenHelper {
private static final String dbName="dbName";
private Context context;
private SQLiteDatabase db;
private final static int version = 1;
public static final String SurveyTbl = "CREATE TABLE SurveyTbl (SurveyId TEXT PRIMARY KEY, Idref TEXT, SurveyDate TEXT)";
public DataHelper(Context context) {
super(context, dbName, null, version);
this.db = getWritableDatabase();
this.context = context;
Log.i("", "********************DatabaseHelper(Context context)");
}
#Override
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL(SurveyTbl);
} catch (Exception e) {
Log.i("", "*******************onCreate");
}
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
try {
db.execSQL("ALTER TABLE HandpumpSurveyTbl ADD COLUMN NalYozna TEXT");
} catch (Exception e) {
Log.i("", ""+e);
}
onCreate(db);
}
}

I didn't get to see your Quiz table schema, but I assume it has fields like "question", "answer", "favorites", and some kind of a unique primary key to identify each question, which I will just call rowId for now.
// after renaming the old table and adding the new table
db.execSQL("UPDATE new_quiz SET new_quiz.favorites = old_quiz.favorites where new_quiz.rowId = old_quiz.rowId");
That will update only the rows of the new quiz table that match the old quiz table, and set the favorites value from the old quiz table.
I assume you have some kind of a unique identifier to identify each question, so instead of the rowId above, you'll use that (question number or something).

For who don't know yet how to upgrade the version of the SQLite when upgrading the database schema for example, use the method needUpgrade(int newVersion)!
My code:
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
if(newVersion>oldVersion){
db.execSQL(scriptUpdate);
db.needUpgrade(newVersion);
}
}

ALTER TABLE mytable ADD COLUMN mycolumn TEXT
In your onUpgrade method, it would look something like this:
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String upgradeQuery = "ALTER TABLE mytable ADD COLUMN mycolumn TEXT";
if (newVersion>oldVersion)
db.execSQL(upgradeQuery);
}

Example, how to drop a table and create a new table without losing data by using a temporary table:
db.execSQL("CREATE TEMPORARY TABLE temp_table (_id INTEGER PRIMARY KEY AUTOINCREMENT, col_1 TEXT, col_2 TEXT);");
db.execSQL("INSERT INTO temp_table SELECT _id, col_1, col_2 FROM old_table");
db.execSQL("CREATE TABLE new_table (_id INTEGER PRIMARY KEY AUTOINCREMENT, col_1 TEXT, col_2 TEXT, col_3 TEXT);");
db.execSQL("INSERT INTO new_table SELECT _id, col_1, col_2, null FROM temp_table");
db.execSQL("DROP TABLE old_table");
db.execSQL("DROP TABLE temp_table");