SQLite Learning (continue to update)

SQLite is a lightweight database, integrated in Android, below to share their own learning.

There are some good instructions to use when accessing the information:
The basic curd statement

The following SQL statement gets 5 records, skipping the previous 3 recordsSelect* fromAccount limit5Offset3OrSelect* fromAccount limit3,5Insert statement:Insert  intoTable name (field list)Values(Value list). Such as:Insert  intoPerson (name, age)Values(' ATM ',3) UPDATE statement:UpdateTable nameSetField name = valuewhereThe conditional clause. Such as:UpdatePersonSetName= ' ATM 'whereId=1Delete statement:Delete  fromTable namewhereThe conditional clause. Such as:Delete  fromPersonwhereId=1

The difference between getwritabledatabase () and Getreadabledatabase ()

getWritableDatabase()和getReadableDatabase()方法都可以获取一个用于操作数据库的SQLiteDatabase实例。但getWritableDatabase() 方法以读写方式打开数据库，一旦数据库的磁盘空间满了，数据库就只能读而不能写，倘若使用getWritableDatabase()打开数据库就会出错。getReadableDatabase()方法先以读写方式打开数据库，如果数据库的磁盘空间满了，就会打开失败，当打开失败后会继续尝试以只读方式打开数据库。注意：getWritableDatabase()，getReadableDatabase的区别是当数据库写满时，调用前者会报错，调用后者不会，所以如果不是更新数据库的话，最好调用后者来获得数据库连接。 

A simple description of the cursor

CursorgetCount()moveToFirst()moveToNext()isAfterLast()getColumnNames()getColumnIndex()getString()，getInt()requery()close() 方法释放游标资源；

The specific code:

First: How to create a database
Create databases and tables.
The default save path for the database is: "data/data/com.example.sqlitetest/databases/"
Com.example.SqliteTest is his own project.

 Public  class dbopenhelp extends sqliteopenhelper {     Public Dbopenhelp(Context context) {Super(Context,"User_atm.db",NULL,1);//TODO auto-generated constructor stub}@Override     Public void onCreate(Sqlitedatabase db) {//TODO auto-generated method stubStringBuilder strSQL =NewStringBuilder (); Strsql.append ("CREATE TABLE IF not EXISTS user_info ("); Strsql.append ("user_id INTEGER PRIMARY KEY autoincrement not NULL,"); Strsql.append ("User_age INT not NULL,"); Strsql.append ("user_name VARCHAR () not NULL)");    Db.execsql (Strsql.tostring ()); }@Override     Public void Onupgrade(Sqlitedatabase DB,intOldversion,intNewVersion) {//Database modification is done here, such as adding table fields}

Here is the code for adding and deleting changes and transactions:

 Public classservicetest {///delete and change    //Get the databaseDbopenhelp Dbopenhelp; Public servicetest(Context context) {super (); This. Dbopenhelp =NewDbopenhelp (context); }//Start transaction     Public void transactiontest() {Sqlitedatabase db = Dbopenhelp.getwritabledatabase (); Db.begintransaction ();Try{Db.execsql ("Update user_info set user_age=user_age+1 where user_id=10"); Db.execsql ("Update user_info set user_age=user_age-1 where user_id=11");        Db.settransactionsuccessful (); }finally{db.endtransaction ();} }//Increase     Public void Save(UserInfo UserInfo)        {Sqlitedatabase db = Dbopenhelp.getwritabledatabase (); Db.execsql ("INSERT into User_info (user_id, user_age, user_name) VALUES (?,?,?)",NewOBJECT[]{USERINFO.GETUSER_ID (), Userinfo.getuser_age (), Userinfo.getuser_name ()}); }//Delete     Public void Delete(Integer user_id)        {Sqlitedatabase db = Dbopenhelp.getwritabledatabase (); Db.execsql ("Delete from User_info where user_id=?",NewOBJECT[]{USER_ID}); }//Modify     Public void Update(UserInfo UserInfo)        {Sqlitedatabase db = Dbopenhelp.getwritabledatabase (); Db.execsql ("Update user_info set user_age=?,user_name=?" where user_id=? ",NewObject[]{userinfo.getuser_age (), Userinfo.getuser_name (), userinfo.getuser_id ()}); }//Enquiry     PublicUserInfoFind(Integer ID)        {Sqlitedatabase db = Dbopenhelp.getreadabledatabase (); cursor cursor = Db.rawquery ("SELECT * from User_info where user_id=?",NewString[]{id.tostring ()});if(Cursor.movetofirst ()) {intuser_id = Cursor.getint (Cursor.getcolumnindex ("user_id"));intUser_age = Cursor.getint (Cursor.getcolumnindex ("User_age")); String user_name = cursor.getstring (Cursor.getcolumnindex ("user_name"));return NewUserInfo (user_id, user_name, user_age); } cursor.close ();return NULL; }}

Visual Database management tools –sqlite Expert Professional
You can download it on the Internet.
After downloading, open the software and enter the main interface:

The middle Red box section is for importing and deleting databases.

In the new table.

There are a number of features that can be re-imported to the device (the path that starts everywhere) when you're done modifying it.

view the database with cmd
Open the database under the development path

Simple database operation, query a table.

Also in the study, such as database monitoring, database triggers and so on. will be updated further.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

SQLite Learning (continue to update)