Essentially, this class can be thought of as representing the database model. Instances of this class can then be created within the activity and database handler and passed back and forth as needed. This is actually a very simple class capable of holding product ID, product name and product quantity values, together with getter and setter methods for accessing these values. In order to implement this interaction in a structured way, a third class will need to be implemented to hold the database entry data as it is passed between the activity and the handler. The database handler will be a subclass of SQLiteOpenHelper and will provide an abstract layer between the underlying SQLite database and the activity class, with the activity calling on the database handler to interact with the database (adding, removing and querying database entries). Once completed, the application will consist of an activity and a database handler class. The database schema for the products table is outlined in Table 48-1: Column Data Type productid Integer / Primary Key/ Auto Increment productname Text productquantity Integer The productid column will act as the primary key and will be automatically assigned and incremented by the database management system. Each record in the database table will contain a unique product ID, a product description and the quantity of that product item currently in stock, corresponding to column names of “productid”, “productname” and “productquantity” respectively. The name of the database will be productID.db which, in turn, will contain a single table named products. The idea behind this application is to allow the tracking of product inventory. if distinct is passed as true Cursor data set will not have any duplicate row.As is probably evident from the user interface layout designed in the preceding chapter, the example project is a simple data entry and retrieval application designed to allow the user to add, query and delete database entries. Most of the parameters in query overloaded functions are optional except from table and distinct any of other parameters can be passed as null. public Cursor query (boolean distinct, String table, String columns, String selection, String selectionArgs, String groupBy, String having, String orderBy, String limit).public Cursor query (String table, String columns, String selection, String selectionArgs, String groupBy, String having, String orderBy).public Cursor query (String table, String columns, String selection, String selectionArgs, String groupBy, String having, String orderBy, String limit).It returns Cursor object so Cursor is a result-set with queried data, it provides different functions really helpful while reading data.įollowing are some overloaded query functions: query() method is overloaded with different set of parameters. SQLiteDatabase class provides query() method to read data from table. Read(select):Reading from a database table is bit different from other functions like insert,update and delete. Important Note: If you want to remove all rows and require count of deleted ones also then pass 1 as whereClause. delete function will return number of affected row if whereClause passed otherwise will return 0. Here whereClause is optional, passing null will delete all rows in table. Public class SqliteManager extends SQLiteOpenHelper ĭb.delete( "Items", whereClause, whereArgs) Whenever we need to create a database we have to extend SQLiteOpenHelper class as follows: /**A helper class to perform database related queries*/ SQLiteOpenHelper is an abstract class with two abstract methods onCreate(SQLiteDatabase db) and onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) and many more database helpful functions. One writing raw queries and another is using parameterized functions or we can say parametrized queries.Ĭreate: Creating a database is very simple in android by using SQLiteOpenHelper class. While using SQLite there could be two different ways to perform different operations like create, read, update and delete. Android os has its own implementation to perform CRUD (Create, Read, Update, Delete)operations, so Android provides set of classes available in android.database and packages. SQLite is a structure query base database, hence we can say it’s a relation database. Android provides different ways to store data locally so using SQLite is one the way to store data.
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