SQL的not exists使用

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create table if not exists a(id varchar(10));

//或者在SQLite中写

package sn.len.mp34player.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;public class DBOpenHelper extends SQLiteOpenHelper {private static final String DBNAME="music.db";private static final Integer DBVERSION=1;public DBOpenHelper(Context context) {super(context, DBNAME, null, DBVERSION);}@Overridepublic void onCreate(SQLiteDatabase conn) {String SQL="create table if not exists music(" +"id integer primary key autoincrement," +"filepath varchar(40)," +"filesize varchar(4)," +"timeLength varchar(50)," +"filename varchar(10)," +"author varchar(10)," +"musicalbum varchar(10)," +"musictype varchar(10)," +"year varchar(10));";conn.execSQL(SQL);Log.i("SQL", SQL);}@Overridepublic void onUpgrade(SQLiteDatabase db, int arg1, int newVersion) {db.execSQL("DROP TABLE IF EXISTS music");onCreate(db);}}

create table sndemos(id int primary key auto_increment,name varchar(20),pass varchar(20) not null,unique (pass));//如果有相同记录就不插入，否则插入insert ignore into sndemos(name,pass) values('xx','xx');