Basic use of SQLite database

The use of small databases built into Android is basically consistent with the use of SQL sever;

The basic process of creating a SQLite data is as follows, which requires implementation of the Sqlopenhelper database Management assistant interface. As follows: Create a new Mysqliteopebhelper class

1  Public classMysqlitehelperextendsSqliteopenhelper {2     //construct a Sqliteopenhelper3      PublicMysqlitehelper (context context, String name, Sqlitedatabase.cursorfactory factory,intversion) {4         Super(context,name,factory,version);5     }6 7 @Override8      Public voidonCreate (Sqlitedatabase db) {9         //Create a database and table (Id,name,age), where the primary key is ID, the self-increment formTenDb.execsql ("CREATE TABLE MyTable (ID integer primary key autoincrement,name text,age integer)"); One     } A  - @Override -      Public voidOnupgrade (Sqlitedatabase db,intOldversion,intnewversion) { the         //Database Updates -     } -}

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Instantiate a database management helper instance in the activity, and then create a DB instance. Getreadabledatabase () and getwirtabledatabase () can create a sqlitedatabase, but two methods are different, the former creates a database that opens the database in read-write mode, and when the disk is full, Will fail, reopening will open the database in read-only mode, which creates a database that is open to read and write, and fails when the disk is full, so it is generally recommended to use the Getreadabledatabase () method to create the database. The following example lists the common methods of the database.

1Mysqlitehelper Mysqlitehelper;//declare a Database management helper Object2Sqlitedatabase database;//declare a Database object3 4     //constructs a Database management helper Object5Mysqlitehelper=NewMysqlitehelper ( This, "TestDB",NULL, 1);6     //This method creates a database that can read and write, the disk is full and will automatically change mode to read-only mode, getwritabledatabase () Full error7Database=mysqlitehelper.getreadabledatabase ();8     //Create a data table9Database.execsql ("CREATE TABLE MyTable (ID integer primary key autoincrement,name text,age integer)");Ten     //Add data (first method) OneContentvalues contentvalues=Newcontentvalues (); AContentvalues.put ("id", 1); -Contentvalues.put ("name", "Old King next Door"); -Contentvalues.put ("Age", 30);; theDatabase.insert ("MyTable",NULL, contentvalues); -     //Add data (method two) -String intsert= "Intsert into MyTable (id,name,age) value (1,\" next door Lao Wang ", 30)"; - Database.execsql (intsert); +     //Delete data (delete table Mytable,id=1 series data from that line) (method one) -Database.delete ("MyTable", "id=?",Newstring[]{"1"}); +     //Delete Data 9 method two) AString delete= "Delete from mytable where id=2"; atDatabase.execsql (delete);//Execute SQL statement -     //Query data (returns a pointer index to invoke the corresponding method to query the data) -Cursor cursor=database.query ("MyTable",Newstring[]{"id", "name", "Age"},NULL,NULL,NULL,NULL,NULL); -      while(Cursor.movetonext ()) { -         intIdindex=cursor.getcolumnindex ("id"); -         intId=Cursor.getint (idindex); in  -         intNameindex=cursor.getcolumnindex ("name"); toString name=cursor.getstring (nameindex); +  -         intAgeindex=cursor.getcolumnindex ("Age"); the         intAge=Cursor.getint (ageindex); *  $String result=id+ "" +name+ "" +age+ "\ n";Panax Notoginseng     } -     //Modifying Data theContentvalues contentvalues1=Newcontentvalues (); +Contentvalues1.put ("id", 3); AContentvalues1.put ("name", "Little King Next Door"); theContentvalues1.put ("Age", 15); +Database.update ("MyTable", ContentValues1, "id=?",Newstring[]{"1"}); -     //Close the database $Database.close ();

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Basic use of SQLite database