Android:SQLite

1. What is SQLite?

        SQLite is an in-process library that implements a self-sufficient, serverless, zero-configuration, transactional SQL database engine. It is a zero-configuration database, which means that unlike other databases, you do not need to configure it in the system. Like other databases, the SQLite engine is not a stand-alone process and can be statically or dynamically linked according to application needs. SQLite directly accesses its storage files.

2. Features of SQLite

             Lightweight, no configuration required, localized

3. Create a database

                Create a new class and inherit SQLiteOpenHelper

                Implement two abstract methods onCreate() onUpgrade() Create a constructor with parameters

                Create database in constructor

                In the onCreate() method, create the table and insert data

 In the mobile phone, use the package name to identify the software's

        SQLite data type

type	SQLite	Java
integer	INTEGER	byte, short, int, long
floating point	REAL	float, double
string	TEXT	String
boolean string	BLOB	boolean

3. SQLite CRUD

        1. Query (there are three methods for receiving result sets: List<Object[ ]>, List<entity class>, List<Map<String,int>>)\

             Using entity class method:

SQLiteDatabase db = dbHelper.getWritableDatabase();

List<User> list = new ArrayList<>();
Cursor cursor = db.rawQuery("select * from user_table");
while (cursor.moveToNext()) {
	String account = cursor.getString(cursor.getColumnIndex("account"));
    String pwd= cursor.getString(cursor.getColumnIndex("pwd"));
    list.add(res);
}
cursor.close();
return list;

2. Update (addition, deletion, modification)

SQLiteDatabase db = dbHelper.getWritableDatabase();
//删除
db.execSQL(""delete from test where account = ?", new String[]{String.valueOf('123')}");
//增加
db.execSQL("insert into test values(?,?)",new String[]{account,pwd});
//修改
db.execSQL("update test set pwd= ? where account= ?", new String[]{"456",String.valueOf(132)});