Android Notes (41) data storage in Android--sqlite (iii) SELECT

SQLite implements queries through query, which defines query conditions through a series of parameters.

Description of each parameter:

Query () method parameters	corresponding SQL section	Describe
Table	From table_name	Table name
Colums	Select Column1,column2	Array of column names
Selection	where column = value	Conditional clauses, equivalent to where
Selectionargs	-	Parameter array for conditional statements
GroupBy	Group BY column	Group
Having	Having column = value	Grouping conditions
By	ORDER BY Column,column	Sort class
Limit		Limitations of paged Queries
Cursor		The return value, equivalent to the result set resultset

There are also a number of ways to target cursors (cursor)

Method name	Method description
GetCount ()	Total number of records
IsFirst ()	Determine if the first record
Islast ()	Determine if the last record
Movetofirst ()	Move to the first record
Movetolast ()	Move to the last record
Move (int offset)	Move to the specified record
MoveToNext ()	Move to Next record
Movetoprevious ()	Move to previous record
Getcolumnindex (String columnName)	Gets the int type value of the specified column index

Here's an example to illustrate the query in SQLite:

Query with no parameters

Mainactivity.java

 PackageCn.lixyz.sqlite;Importandroid.app.Activity;Importandroid.content.ContentValues;ImportAndroid.content.Context;ImportAndroid.database.Cursor;Importandroid.database.sqlite.SQLiteDatabase;Importandroid.database.sqlite.SQLiteDatabase.CursorFactory;ImportAndroid.database.sqlite.SQLiteOpenHelper;ImportAndroid.os.Bundle;ImportAndroid.util.Log;ImportAndroid.view.View;ImportAndroid.widget.Button;ImportAndroid.widget.EditText;ImportAndroid.widget.Toast; Public classMainactivityextendsActivity {PrivateEditText name, age; PrivateButton Insertbutton, Selectbutton; Privatesqlitedatabase database; PrivateMysqliteopenhelper Msop;  PublicString Inputsex; @Overrideprotected voidonCreate (Bundle savedinstancestate) {Super. OnCreate (savedinstancestate);        Setcontentview (R.layout.activity_main);        Findview (); Msop=NewMysqliteopenhelper ( This, "User.db",NULL, 1); Database=msop.getreadabledatabase (); }    Private voidFindview () {name=(EditText) Findviewbyid (r.id.name); Age=(EditText) Findviewbyid (r.id.age); Insertbutton=(Button) Findviewbyid (R.id.insertbutton); Selectbutton=(Button) Findviewbyid (R.id.selectbutton); }     Public voidClickbutton (view view) {Switch(View.getid ()) { CaseR.id.selectbutton:selectdata ();  Break;  CaseR.id.insertbutton:insertdata ();  Break; }    }    Private voidInsertData () {String inputage=Age.gettext (). toString (); String InputName=Name.gettext (). toString (); Contentvalues CV=Newcontentvalues (); Cv.put ("Name", InputName); Cv.put ("Age", Inputage); Database.insert ("User",NULL, CV); Toast.maketext (mainactivity. This, "Insert succeeded", Toast.length_short). Show (); Age.settext (""); Name.settext (""); }    Private voidSelectdata () {Cursor C= Database.query ("User",NULL,NULL,NULL,NULL,NULL,NULL); if(C.movetofirst ()) { Do {                intid = c.getint (c.getcolumnindex ("id"))); String name= C.getstring (C.getcolumnindex ("name")); String Age= C.getstring (C.getcolumnindex ("Age")); LOG.D ("Tttt", "id=" + ID + ", name =" + Name + ", age =" +Age ); }  while(C.movetonext ());    } c.close (); }    classMysqliteopenhelperextendsSqliteopenhelper {Private Static FinalString create_user = "CREATE table USER (ID integer primary key autoincrement,name text,age text)"; PrivateContext Mcontext;  PublicMysqliteopenhelper (context context, String name, Cursorfactory factory,intversion) {            Super(context, name, Factory, version); Mcontext=context; } @Override Public voidonCreate (Sqlitedatabase db) {db.execsql (create_user); } @Override Public voidOnupgrade (Sqlitedatabase db,intOldversion,intnewversion) {            //TODO auto-generated Method Stub        }    }}

Activity_main.xml

<LinearLayoutxmlns:android= "Http://schemas.android.com/apk/res/android"Xmlns:tools= "Http://schemas.android.com/tools"Android:layout_width= "Match_parent"Android:layout_height= "Match_parent"android:orientation= "vertical"Tools:context=". Mainactivity " >    <EditTextAndroid:id= "@+id/name"Android:layout_width= "Match_parent"Android:layout_height= "Wrap_content"Android:hint= "Enter Name" />    <EditTextAndroid:id= "@+id/age"Android:layout_width= "Match_parent"Android:layout_height= "Wrap_content"Android:hint= "Input Age" />    <ButtonAndroid:id= "@+id/insertbutton"Android:layout_width= "Match_parent"Android:layout_height= "Wrap_content"Android:onclick= "Clickbutton"Android:text= "click Insert" />    <ButtonAndroid:id= "@+id/selectbutton"Android:layout_width= "Match_parent"Android:layout_height= "Wrap_content"Android:onclick= "Clickbutton"Android:text= "click Query" /></LinearLayout>

Insert a few data first, then click the Query button:

　　

Android Notes (41) data storage in Android--sqlite (iii) SELECT