android studio sqlite foreign key references

#Android studio sqlite foreign key references how to
#Android studio sqlite foreign key references full
#Android studio sqlite foreign key references android
#Android studio sqlite foreign key references password

String Group by: A string specifying group by clause.String selection args: The parameters of the WHERE clause.String WHERE clause: where clause, if none pass null.

String columns: The projection of the query, i.e., the columns to retrieve.

String Table Name: The name of the table to run the query against.

The db.query has the following parameters: Public void onCreate(SQLiteDatabase db) Ĭursor c=db.query(viewEmps, columns, colDeptName+ ' =?', Our class will have the following members:

onUpgrade(SQLiteDatabse db, int oldVersion, int newVersion): invoked when we make a modification to the database such as altering, dropping, creating new tables.

onCreate(SQLiteDatabase db): invoked when the database is created, this is where we can create tables and columns to them, create views or triggers.

This class provides two methods to override to deal with the database: The first step is to create a class that inherits from SQLiteOpenHelper class.

First, we will create a class that handles all the operations required to deal with the database such as creating the database, creating tables, inserting and deleting records and so on.

#Android studio sqlite foreign key references android

ViewEmps: to display employees and their relative departments.īy default, SQLite on Android does not have a management interface or an application to create and manage databases from, so we're going to create the database ourselves by code.In this tutorial, we will create a simple database application to store employees data.

#Android studio sqlite foreign key references full

SQLite Full Unicode support is optional and not installed by default.

Referential integrity is not maintained in SQLite, there is no FOREIGN KEY constraints or JOIN statements.

Data type integrity is not maintained in SQLite, you can put a value of a certain data type in a column of another datatype (put string in an integer and vice versa).

Things to consider when dealing with SQLite: SQLite is a lightweight transactional database engine that occupies a small amount of disk storage and memory, so it's a perfect choice for creating databases on many mobile operating systems such as Android, iOS. OR if you want to keep that match_id, then the two participant_ids in the match table are not needed.Android default Database engine is Lite. It's never good to have duplicate information in a SQL table, they could go out of sync, and constraints could become hell (when deleting). That will only duplicate the participants id from your match table. No need for the match_id in participant table. When you do your query to select or insert, be sure to save the correct ids in your table, and that will work. There's no problem at all in having two links to the same table. + 'FOREIGN KEY(Participant2_id) REFERENCES '+ participantTableName+'(Participant_id)' + 'FOREIGN KEY(Participant1_id) REFERENCES '+ participantTableName+'(Participant_id),' + '(Match_id integer primary key autoincrement, ' ' FOREIGN KEY(match_id) REFERENCES '+ matchTableName+'(Match_id),' + 'FOREIGN KEY(player_id) REFERENCES '+ playerTableName+'(Player_id),' + + '(Participant_id integer primary key autoincrement, ' + + '(Match_id integer primary key autoincrement, ' + MyDB.execSQL('CREATE TABLE IF NOT EXISTS '

#Android studio sqlite foreign key references password

'UserName VARCHAR, Password VARCHAR, Experience INTEGER, Rating INTEGER) ') + ' (Player_id integer primary key autoincrement, ' +

#Android studio sqlite foreign key references how to

I am trying to create the Match table so that it can reference two Match participants but I am unsure how to do this.Ĭode I have done to create tables myDB.execSQL('CREATE TABLE IF NOT EXISTS ' Then finally a Match participant table which will have an id, player_id (foreign key), match_id (foreign key) and a score which is an integer. I have a player table which contains an id, name password. I am trying to store match results in a database.